The squeal has been on at least two tapes, but nothing on the one currently in the 9000.
This may require a bit more investigation, but I’ll bet you are right; it is the tapes breaking down with age.
No I have not carefully cleaned the tape path in the 9000, as a cursory inspection did not show any dirt build up. I did clean the 8004, but that unit has had a LOT more use compared with the 9000. On the other hand, the 8004 plays all my tapes, the 9000 doesn’t.
Perhaps I just need a little more attention to detail. Thanks for the information and the tip!
Jeff