This has happened to me a number of times. The tape playing machinery seems to be the fragilest (most fragile?) part of the system and most subject to the kinds of problems you describe. I have learned the hard way that "repair" is now more of a theoretical concept than a real possibility for electronics. In the old days I would try finding a competent, honest, repairperson (talk about oxymorons), but since then I have repeatedly bitten the bullet and simply replaced the offending boom box, or tape deck, or tape player.