Symptoms of failing dynamic drum on JVC S-VHS VCRs?
 

What symptoms actually occur when the dynamic drum system is bad or is going bad on the 7600/8600/9600 series VCRs?

I am aware of the thread about how to fix them, but I haven't found a definitive post that describes the symptoms how to know when they are bad.

I'd prefer not to mess with them if they aren't already broken, though I understand them going bad eventually is quite likely.

Thanks in advance!

Mostly kicking out the tape within seconds of ingest. You see lots of those.