New SKILSAW 5995 used once to cut 1/4 inch plywood, no problem. Several months pass and I went to cut a pine board, the blade touched the wood and stopped. I recharged the batteries and tried again, two fully charged batteries, the blade touched the wood and it stopped dead.

Sounds like your blade is not secured to the drive shaft. Hold blade against a piece of wood and tighten bolt.

Is the blade the correct one for the type of wood you are cutting?? There will be recommendations on the saw blade. Finer toothed blades are for plywood, etc. Aggressive or large tooth blades are for thicker wood.

Unfortunately that is just to thick of material to cut with a jig saw blade. Plywood is made up of several layers and your blade is trying to follow the grain on one of them. You can try a metal blade and high motor speed low travel rate, but it will quickly heat up the blade and warp it making your problem worse if you don't stop often. If you are trying to make straight and curved cuts, I have the best luck with a rotary cutter such as the roto zip, but plywood easily snaps the bits.

I am a retired contractor.
I have a shop with a 10" table saw.
And I have opinions about safe operation.

For safety, turn saw off when making adjustments.

1) Raise blade:
There is a handle you turn to raise the blade.
If you are cutting 1/2" plywood, then set your blade at 3/4" or a bit more.
Keep blade low and away from hands.
Keep hands high and away from blade.

For 1-1/2" thick 2x4, I usually set the saw at 1" and run the board through, and then flip the board over and run it through again, taking 2 passes to make really thick cuts.



2) Blade angle
There is a second handle you turn to set blade at an angle up to 45 degrees
Angle cannot be set if saw blade is fully raised >> lower blade to half way or less and experiment.
Angle cuts are difficult if wood is not perfectly flat and square, or too long or too short (boy is that helpful ... but cutting angles takes some experimentation)

3) Table Guide
You stand behind power saw to operate
The saw table guide is on left side of blade and clamps across the table
The guide markings show inches >>> these are usually approximate
To set guide for accuracy, measure distance from blade to saw guide, and then clamp guide down.

4) Push sticks push sticks push sticks and other safety stuff
Let me emphasize safety first last and always
A table saw will chop your fingers off in a blink
On the plus side, I hear it doesn't hurt. But OMG.
There is a very strong human instinct to reach in with your hand when working on stuff
Train your mind >> if the saw is running, do not lean or reach into the saw
If a board is stuck >>> turn off the saw and wait for full stop
If you wear baggy clothes of a loose shirt, the saw will grab you and pull you in too fast for you to react
Keep your clothes tight and your arms bare

Always use push sticks or push boards::

Notice the saw blade is set low
Two push sticks are used to assist when cutting short board > one stick holds down the board ahead of blade, the other stick is pushing board through saw.
Keep your hands away from the blade no matter what.
The person stands behind and to the side of the board being cut.
The cut wood is supported by a catch table (in this case there are rollers)

Where to stand
Obviously you stand behind the saw to cut wood, and sometimes with long pieces, you can move in front and pull them through, and sometimes with large plywood you stand kinda back and to the side.

Why not stand directly behind a saw? Because saws throw stuff back.
When 'ripping' a board lengthwise as shown in photo above, if the saw catches the board just right, it will throw it backwards like a spear.

If a board 'binds' the saw causing saw blade to stop, then turn off saw, back up the board, and cut again.

Crosscut guide
The saw comes with a T-shaped guide that fits into a groove.
This is a 'push stick' >>> you use it to cross cut a board, and it lets you stand to the side of the saw blade so things wont flip back on you
When using the cross cut guide, remove the table guide that clamps across the saw, or push the table guide WAY back so pieces don't get caught in a bind and the blade flips up the piece and hits you in the face
Remember, the saw throws everything backwards

The saw is strong and fast, and you are best when traveling slow and without rush around your strong friend.

Use a backing board, such as high grade 3/4 inch plywood under the board you are planing, and you should be able to get down to 1/16, depending on the stability of the board you are planing. Take light cuts and flip it over to cut on both sides. Sounds like you might be making a guitar? Good luck.

I would replace the brushes on the motor, that is the first cause of arcing. The armature may be worn down too. Still a pretty easy inexpensive repair.

Fine tooth or plywood cutting blade.

This depends on the type of wood you are cutting. Hardwoods , like oak, will dull the blades faster and require a change after about 3 months if used daily 8x7 but you can get a longer cutting time IF the blades are carbide steel. You can add life to the saw teeth by keeping them clean and free of sap buildup too.
Specially when cutting pine.

The 1590, like several Bosch jigsaws, has a selector switch to choose the type of cutting action. You have to choose the appropriate cutting action, either straight or oscillating, to accommodate the material you cut and the blade you cut with. For instance, if using a very slender blade for clean curved cuts in wood, a slight oscillating motion ( setting II or III) reduces friction on the blade. 
If you choose the straight cutting action you get maximum accuracy, but drastically increase the friction because the blade is held firmly to the roller bearing.  A slender blade can handle that for brief periods, (say... less than thirty seconds) in soft, thin wood with a straight cut. In hard woods or engineered wood products ( plywood, MDF etc.) the thin blade will heat up and bend. 
You can reduce friction by choosing an oscillating cutting motion, or you can use a larger, sturdier blade. The "Aggressor" blades do not cut as smoothly as the "clean" blades, but they cut faster and are stronger. To cut thick wood ( 4x4 ) or a long cut in engineered material, that is the blade I use. Select number III or number II for 'type-of-cut' and use a bigger blade. See if that stops the "bucking."
Good luck!

Here a few examples: * 5 inch trim saws, usually with a fine-toothed blade and often with the blade located on the left side of the motor, for easy viewing of the blade path. These are available in 120V, AC models, and rechargeable battery models in various DC voltages. * 6 1/2 inch saws, as shown in the illustration above, used for cutting to length nominal lumber for construction, as well as ripping lumber, and cutting plywood or composite material. * 7 1/4 inch saws, often call skillsaws, from the name of a major circular saw manufacturer, Skill. These are the backbone of the construction industry, used for cutting lumber up to 2 1/4 inch thick. They are used for cutting framing lumber to length, and ripping lumber. They also have a number of optional blades which can be used for cutting composite materials, concrete, ferrous and nonferrous metal sheeting, pipe, tubing, and even cold-rolled steel bar stock. * 8 and 10 inch saws, used for cutting to length larger lumber or timbers, up to 4 inches thick. These are heavier, more cumbersome tools used mostly in industrial work. * Worm-drive saws have a gearbox with a worm-geardrive, and are found in 7 1/4 inch models which are most commonly used for ripping lumber or cutting plywood decking or sheathing. They typically have the blade on the left side of the machine, to make watching the blade path easier when cutting parallel to the edge of a wide sheet of plywood.