Wavetek 9100 Scope Opt Failure Questions

[Testtech]

I have a Wavetek 9100 with the Opt 250 scope cal board.
This unit has self test failures in the scope board as shown in the pictures. This has been an intermittent problem, when working, it works correctly. But this is difficult to duplicate.
The basic calibrator functions work correctly at all times, the problem seems to be confined to the scope board.
If the self test is run repeatedly, the "Measured" values will be different.
Anyone have experience with this instrument?