Kyocera FS-C8520 Wierd Problem

[tee]

I would try installing the print monitor on a computer and
see if it is out of toner,paper, jammed up,pm time or other error.
Since you can't get in service mode, this should tell you if it is simple or
time to replace pcbs. A jam state stops everything.

[Alexsiskm]

For me it looks like RAM problem.