I too have had the same types of jams. First it was the paper tray
sensor - have to keep removing the paper and tapping the sensor lever.
That would then keep it happy for the session. Now, it needs to be
tapped every sheet. Not acceptable.

Second, the tray wouldn't rise up to allow the paper to feed. The
trick of tapping/banging the back left corner of the tray seems to work
- for the session. Probably loosens the solenoid moving parts so it can
work properly.

Third, once in a while the crumpled paper - not feeding at a later
position while still pushing from an earlier one. But hasn't happened
for a long time.

Fourth, media jam/transfer roller. This one I can't figure out. The
sensor levers (3 that I can find) seem to move fine. I've blown out
each area with air. But I'm always getting that error and the paper out
stops about 1/4" short and the color hasn't transferred properly
(because the process stops when the error is sensed?). This is for the
demo page. If I print the config page which is black and white, it
works fine, comes out, no error.

So it appears to me that the paper sensors have deteriorated somehow.
Is it dust? film? age?. They work sometimes and sometimes not. So they
haven't permanently failed. Seems like just not quite enough "signal"
in a analog sense.

I'd try wiping them with alcohol, but I can't easily get to the actual
led/sensor module to touch with a swab. Even the paper tray sensor
isn't accessable.

So, has anyone discovered why the sensors are intermittent? And how
you fix them?