Sammy,
I had 2 consistent problems with all of these series of decks, which all gave the same symptoms - the first problem I described with the rollers, and the second problem is too much friction on the motor shaft.
To take care of this, you need to remove the motor from the cassette table, and have it sit upright on a flat surface.
If you are lucky enough to have a motor, in which the tiny roller bolt has not seized, you can remove the roller, and then disassemble the motor. Oil the shaft generously with sewing-machine oil (never WD40 or other Water Dispersants). Reassemble the motor, and replace the roller.
If you are unlucky enough (like me) to have a seized bolt, which means that you cannot remove the roller, and therefore cannot disassemble the motor, then you need to be a little more creative in getting the oil onto the motor shaft.
First supply the motor with a 5-6VDC battery source - correct polarity, so the motor turns. You may have to flick the motor roller to get it started.
Then partially fill a hypodermic syringe with oil, and then get the needle tip directly to the shaft at the point where it enters the motor housing - the point of maximum friction. With the shaft rotating, squirt oil at this junction.
Leave the motor running, and after about 5 minutes do it again.
Shut off the DC supply, and leave overnight.
Next morning, repeat the oiling.
Trial and frustrated error has proven this to be the only reliable way of getting enough lubrication into that critical junction.
That's exactly the solution to your "now it works and now it doesn't" problem.
Menahem
Learn from the mistakes of others - you'll not live long enough to make them all yourself!