I can see that the Display board is generating the XYINH signal that should block the analog scope signals from being displayed during the digital interval, however the characters are smearing because the analog signals are not inhibited.
Further, in looking at the way the characters are distorted, it is strictly in the horizontal direction. The top and bottom of the character is never affected, but the left to right placement of the pixels is impaired. That suggests that the flaw is in the Horizontal Amplifier circuitry, which is not acting on the XYINH.
When checking out the rest of the scope, I observed that only the B horizontal plug-in is working, the A plug in does not cause traces. Swapping the actual plug-in modules made it crystal clear that the problem is in the horizontal switch circuitry, just where my other problem is manifesting.
The circuitry in question is on board A9 inside the main body of the scope, not on the plug in boards on the side. It is behind the plug-ins, which suggests that access a real pain. However, when I began disassembling I found that it was brilliantly designed for easy access.
|Card A9 exposed behind metal plate|
|Card A9 seen from underneath|
|Card removed through opening|
|Access from behind plug-ins|