The cable I described developes cracks with age. This causes intermittant connections withint hte cable. I have repaired a number of these units, some of which had the problem you described. Some of these also were "fixed" by replacing the cable. The cable is by no means the only cause of hte problem you describe. The photo trnasistors can be bad, the digital transistors (DTC) that "digitize" the transition can be faulty as well. The bottom line here is that there are many potential causes of the problem. Experience will provide you with clues (as I and others posted here).

A cam gear off by 1 tooth can cause this problem as well. Obtain the service manual which contains the alignment marks to verify proper alignment of the tray as well.

Dan