Have one where the bottom 1/4 of the copy is back grounding big time.It's not a cleaning blade problem and it's before the fuser. I clean everthing but it didn't help. I wondering if it could be the drum It looks fine and it's OEM. Thanks for any input.

Are all the LED's in the cleaning lamp working?

Sorry, dumb suggestion . You did say the bottom quarter , didn't you.

It sounds like a faulty drum to me.
Regards...Venom

Could be main charge or grid shorting out. Check the charges always good to replace the wires it is a easy place to start.

I'd say charger too. Take the transfer charger apart and check under the housings. Might see some whitish areas where charger is arcing.