First 5 stitches my thread tabgles

That is tension. Sounds like you need to tighten the upper tension slightly to bring the bobbin thread up. The tension is correct when the upper and bobbin threads meet in the middle of the fabric. Also, tension will not always be constant. It may need to change as you change fabrics, thread, and as your machine ages, so it is best to get comfortable with adjusting the tension for each project.

Sewing Lesson 10 How to Fix Tension on Your Sewing Machine

Understanding Thread Tension Threads

How to Adjust the Tension on Sewing Machine

According to the manual, you should not need to adjust the bobbin tension (and I located other sites which stated the bobbin tension cannot be adjusted on this machine). Apparently, all the tension adjustment is accomplished through the upper thread::
"EN Thread Tension Upper thread tension Basic thread tension setting: "4". (1) To increase the tension, turn the dial to the next number up. To reduce the tension, turn the dial to the next number down. A. Normal thread tension for straight stitch sewing. B. Thread tension too loose for straight stitch sewing. Turn dial to higher number. C. Thread tension too tight for straight stitch sewing. Turn dial to lower number. D. Normal thread tension for zig zag and decorative sewing. Correct thread tension is when a small amount of the upper thread appears on the bottom side of fabric. Lower thread tension The bobbin tension has been set correctly at the factory, so you do not need to adjust it. Please note: - Proper tension setting is important for strong seams. - There is no single tension setting appropriate for all stitch functions, thread or fabric. - A balanced tension (identical stitches both top and bottom) is usually only desirable for straight stitch construction sewing. - 90% of all sewing will be between "3" and "5". - For zig zag and decorative sewing stitch functions, thread tension should generally be less than for straight stitch sewing. - For all decorative sewing you will always obtain a nicer stitch and less fabric puckering when the upper thread appears on the bottom side of your fabric. 1 A B C 22 D"

Doing further research, I found this statement on a machine review site:
"After reading reviews online from where I've bought my drop-in bobbin machines, I think many of the negative reviews are due to the bobbin thread coming up without laying across the bobbin. It can cause the stitches to look very sloppy and no amount of tension adjusting can fix the stitches."

There are several machine review sites wherein 4423 owners stated their disappointment in the 4423's performance. Some said the machine failed almost immediately and others said the machines developed problems when sewing heavy fabric.

When selecting a stich, there's a button with a triangle with one edge pointing down. There you can select Needle Position and Stitch Length. --PDF manual, page 23

The thread tension has no influence on the stitch length. It just adjusts, where needle thread and bobbin thread 'meet' inside the fabric. A too high tension means, the bobbin thread is pulled trough the fabric and can be seen on the upper (needle) side. A too low tension means, the bobbin thread is not pulled through the fabric and you can see the needle thread on the bobbin side.

Have you changed your needle lately? Have you checked the needle/shuttle timing?

try changing the needle first--make sure the needle is the correct one for the fabric being sewed.
if you've adjusted the top tension & the bottom stitch still looks the same
it's possible that the top tension dial is needing to be checked to see if it's
working correctly

first let's deal with the needle becoming unthreaded, Keeping the needle threaded is easy, always keep thread tails of 3 to 6 inches on the top thread & bobbin at all times, & make sure the thread tail are pulled behind the needle before you start to sew,, this will ensure that the thread will not come out of the needle when you start to sew.

you mention the fabric is thin,, do you have a needle that's right for the fabric your sewing?
thin fabric needs a different needle than blue jeans fabric, check your top tension & see what the setting is on, usually 3 to 5 is good.

when the needle & thread are right for the fabric then the sewing is good.

also clean under the needle plate & bobbin area for loose threads or lint

also it's a possibility that the machine could be out of time & would need to be serviced by a sewing machine repair shop-as they have the tools for the job

Recheck the bobbin to be sure the thread is feeding from the bobbin spool in the correct direction and through the proper guides.

Re-thread the machine with the presser foot up.

Make sure the needle in inserted with the flat side to the back of the sewing machine.

TENSION: As you change projects and start sewing on different weight materials, you should test stitch on a piece of scrap material of the same weight before beginning the actual project so you can adjust your upper tension to that particular fabric. As an example, if you're changing from a denim type fabric to a silky fabric, you would definitely want to make sure the tension is correct and the stitching looks right before you start to sew the garment.

To determine whether the upper tension is too tight or too loose for the fabric you're wanting to use, try the following test. Take a small scrap of the fabric, fold it, and stitch a line ON THE BIAS of the fabric, using different colors of thread in the bobbin and on top. Grasp the bias line of stitching between the thumb and the index finger. Space the hands about 3 inches apart and pull with an even, quick force until one thread breaks. If the broken thread is the color of the thread in the needle, it means that the upper tension is too tight. If the broken thread is the color of the bobbin thread, the upper tension is too loose. If both threads break together and take more force to break, it means that the tensions are balanced.

BOBBIN: The most probable cause of the lower thread breaking is an improperly wound bobbin. Regardless of where you wind the bobbin, inside the machine, on the top of the handwheel or on the front side near the hand wheel, the basic "bobbin" rules apply.

** Always start with an empty bobbin. Never wind one color over another color.
** Don't wind the bobbin so full that it would be tight and hard to insert into the bobbin case. Most machines have an automatic "shut off" when the bobbin gets full, but if yours does not, be careful not to fill it too full.
** Wind the bobbin evenly across and in level layers.
** Never mix different sizes of thread in the bobbin and on the spool, unless you're doing sewing machine embroidery or some specialty type of sewing. Using different weights of thread on the spool and in the bobbin for general sewing will cause ragged stitches as well as other stitching problems.

NEEDLE: Probably 25% of machine repair jobs I go out on, the only problem was that the needle was put in backwards. I know you're probably saying "I've been sewing most of my life and I know how to put the needle in the machine"; however many times a seamstress will get in a hurry and not give the needle a second thought when putting a new one in the machine. If your machine will not pick up the bottom thread or skips stitches badly, in most cases it's because the needle is in wrong.

Each sewing machine requires that the "flat" side of the needle be put in a specific way - facing the front, the back, etc., depending on your particular make and model. If you have a sewing machine that takes a needle that doesn't have a flat side, you'll notice that each needle has a groove in it where the thread lays as it penetrates the fabric. Depending on whether your machine shuttle system faces to the front or to the left, the groove of the needle will also face front or left.

MACHINE THREADING: An additional area to check for stitching problems is whether the sewing machine is threaded properly. Each machine has a certain sequence for threading, and it only takes one missed step in the sequence to cause your machine to skip stitches. If you're in doubt, take the top thread completely out and start all over again.

If it was sewing correctly BEFORE the needle break...why did the needle break in the first place?...and what fixes did you make?
If it sewed properly...what changed?

Cut your upper thread close to the spool...make sure the presser foot is raised and pull the cut off thread section through/out of the machine from the needle area (sewing direction...do not pull the thread backwards!)

Clean out the bobbin area...remove any traces of lint or pieces of thread...look for any broken off needle pieces... brush the bobbin area out....then add a drop of sewing machine oil (but only if your manual says to oil that area).

Remove the needle plate to expose the feed dogs...brush/clean out that area too and add a drop of sewing machine oil...then secure the needle plate back on.
Replace the needle...do it again...yup...some needles arrive bad from the factory. Make sure the needle is inserted and positioned properly. Then thread the machine WITH the presser foot in raised position. (The thread needs to get seated into the upper tensions.)
..with the.presser foot down...thread the new needle.
Oh...and use the correct needle for the thread. (a universal 80/12 is standard).
Thread can cause issues too. Try a different bobbin, or maybe a different spool of thread to see if that makes a difference.

I own this little gem of a machine. It definitely sews a perfect stitch. I'm assuming you own the green 3/4 size machine as denoted by your product number. The half size blue one pictured is incorrect.

Anyway, this machine sews a perfect stitch, due to the oscillating bobbin. Most sewing machines with rotary (drop in) bobbins don't have an easily accessible bobbin tension screw, which means your fabric is usually slightly puckered. Fiddling with only the upper tension helps very little. This frustrates me to no end for sewing long curtains, clothing side seams, etc. Wrong tension causes them to hang with puckers, making them look awful. With the Hello Kitty 3/4 size Janome, there is a screw on the bobbin case which allows you to adjust for every thread diameter perfectly. Always a perfect stitch, if you take the time to adjust this screw.

To adjust the bobbin for a perfect tension, load the bobbin into the bobbin case and thread it through the guide. Holding only the thread between two or three fingers, let the bobbin case dangle below. This will be slightly difficult, because the bobbin will want to fall out of the case. Don't worry, just don't move it around too much and it will stay in long enough for this test. If the metal bobbin case slowly drops lower, unwinding thread as it goes, the thread is too loose. Tighten the screw on the side of the bobbin case a little (about a quarter turn.)

If the bobbin case seems to be dangling firmly, give the thread a gentle tug, lifting up fairly quickly. If it doesn't release a couple of inches of thread, it's too tight, loosen the screw. You know the tension is perfect when a quick, light tug of the thread releases a couple of inches of thread.