I have a treadmill that feels like it's skipping. I adjusted the belt and still skipping. Someone had tld me it was something else but I can't rember what it was. Could you tell mewhat it is? Thank you very much.

First of all lubricate the treadmill. If it didn't workout then try to tension the walking belt.
If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience.
http://electro-medical.blogspot.com/

https://www.youtube.com/watch?v=b1MU7MvBETs
https://www.youtube.com/watch?v=JC72OIKdluY

see the video and proceed according. God bless youlube the rack and pinion of elevation motor, and adjust the small POT attached. see the diagram attached.

not sure if there is a weight limit but did you check the belt tension.
front or rear roller should have an adjustment screw on both sides to tighten the belt. this could be the solution to your problem

3 different possibilities in my opinion:

belt is too loose, belt is too tight, belt is worn out.

Try to lift the belt and get your hand under it in the middle of the deck. If you cannot reach, it is possible that your belt is too tight. Another clue for this would be the belt "curling" on both sides at the edges. Try to loosen the belt, gradually and testing it along the way.

If on the contrary you can easily slide your hand under the belt from one side to the other, it is more likely that the belt is too loose. The squeaking might be due to the belt not being "square" on the deck. Try to loosen it even more until you can slide it with your hands across the deck. And have it aligned evenly at the front and back. Then retighten and adjust the tracking at low speed.
!!! Do not over loosen as the bolts might come out of the back roller.

A worn out belt might squeak and skip when its old.

Remove the motor cover. Run the treadmill and observe the operation. Try walking on the machine and again observe the operation.
There could be 1 of 3 things causing your problem.
1) the motor drive belt may be loose. Tighten or replace the motor belt.
2) the pulley may have broken free from the front roller. Drill a small hole through the pulley into the metal roller on the backside of the pulley, and drive a screw into it. (see picture).
2) the walking belt is too loose. Adjust the walking belt by the rear roller adjustment bolts.
I have also seen the drive pulley come loose from the motor, but that is very rare and unlikely..
If you need someone to service the machine, on the model/serial number tag is a phone number to the manufacturer. They will direct you to the authorized service company in your area.

It might just need a simple adjustment of the running belt that can eliminate the slipping refer to you owner's manual for the procedure. It will be close to all treadmill adjustments.
Here is a generic procedure for adjusting the belt:
If the walking belt slips when walked on. Run the treadmill @ 3 to 4 mph, walk for a few minutes, Using the allen wrench, turn both rear roller adjustment bolts clockwise, 1/4 of a turn. Then repeat adjusting procedure until walking belt is properly tightened.

take the cover off, if the front drive roller continues to turn when the running belt stops, tension the running belt by using the rear adjustment screws. One full turn on each side should do it. If the front roller stops turning but the motor doesn't, tension the drive belt by adjusting the motor back.

If you can stop the belt. You need to be aware that the drive belt can also cause this problem so I suggest that you remove the motor shroud and when you are adjusting whether the front roller is moving and the running belt has stopped (adjust back rollers) or the roller has stopped and motor is rotating ( adjust Drive Belt)

Your treadmill is trying to tell you its due for a tune-up!

This is caused by one of three problems. First and most likely, the walking belt is loose. To tighten the belt, start by locating the two bolts that adjust the rear roller (one on each side of the unit in the back). Run the unit at about 3 mph. Tighten the bolts a 1/4 turn at a time. Make sure that what you do to one side, you MUST do to the other side or the belt will get off center. After you tighten it 1/4 turn, check the belt to see if it is still slipping. If it is then tighten the belt 1/4 turn again. Continue until the belt does not slip, but do not tighten the bolts more than 2 full turns. If it takes more than 2 turns then something else is the problem. The second problem that it could be is the drive belt might be loose. To tighten the drive belt, start by removing the front cover. loosen the bolts around the motor then tighten the drive belt by tightening the motor adjuster bolt. Once the drive belt is tight, tighten the motor back down. The third problem that it could be is the walking belt could be worn and need to be replaced. Let me know if you have any questions.