The most common problem I've heard (2nd hand) is that the rubber belts for the tape drive have degraded. I don't know how replaceable the belts are.
shouldnt be too hard to find replacements. A buddy of mine had me modify an old 80's sony walkman with a fake cassette usb hub that i powered and connected to the pc through the actual walkman. When i opened it up the rubber belt had turned back into tar. If there was a piece of belt that was recognizable as part of the belt and you touched it, it turned to goo. Was a huge pain to clean out of the system and it really stained my hands. Im sure that these could possibly have the same issue. Better to take it apart and replace without trying to play it.
Edited by pimpmaul69, Sat Apr 15, 2017 12:09 AM.