[Eliot Ness]

I decided to clean pinch rollers and capstans, as one of the tapes got chewed up. Totally non invasive procedure. After that the sound goes tftom normal to muffled to none and back. Clearly mechanical but can't fathom for the life of me what I did. Cotton swab over rollers.....and that?
Ruined my plans.....just bought bunch of cassettes.

You're right, that is pretty non-invasive, so my guess is it was just a coincidence that it happened after cleaning.   Well, unless a bit of the cotton swap wound up in the mechanism somehow throwing off the alignment.