Kenmore dryer's drum won't rotate Options - Part II

About 9 months ago, I posted here a description of a problem that was answered in the most helpful manner by Paul:

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The dryer has been in use since then, working almost perfectly - but with a little problem:

After one drying session, I need to wait for it to cool down before I can restart it again.

This problem is very consistent: If the dryer is sufficiently cool, it will start and run till completion or till.. it gets too hot and then stop (before completing the session).

I did notice that starting it is not as easy as it used to be: It seems that the drum has a hard time rotating (mechanically speaking) - and the motor sounds some noise of trying to rotate something that is mechanically stuck. However, if it is cool enough, it will start after a 2-3 seconds.

I suspected the support rollers, but when I took the dryer apart, they looked all even (as if they are new). Each of them rotates freely on its shaft, and when the drum is mounted and rotating I verified that all of them rotate. So, does that rule out the rollers?

Also, if the rollers are gone, why is it temperature dependent?

I could have bought new rollers and see if they solve the problem, but it's a $50 expense which I would like to avoid if not necessary. It could turn out to be the motor (?) or some thermostat... How do I know which?

I did notice that one of the shafts (the rear right one) is worn out... could this be the problem? How can I measure the "freedom" of those support rollers rotation?

Thanks for any tip or idea you can offer! Sam