Roland 308 CPL problems

Hello,
At a Roland 308, the error 74 is shown quite often, sometimes at the plate insertion, sometimes when they are removed. The error always shows at different units.
Is there someone who could advise me on this or whom has encountered this error previously?
Also, the CPL systems have been cleaned and oiled.
There was also a recalibration done with the Service Tools floppy disk.
Could the potentiometers be at fault?
Additionally, I have tightened the bars with 600-800 mA, otherwise the errors are much more frequent.

 

Error 74 is a positioning error. It can also be indicated by a defective potentiometer. Тhe motor current must be 950-1100mA