Failure During Diagnostic Test

When I run the diagnostic test on my HE3 washer, it goes from C00 to C01, water runs out, then the F11 failure comes up. I’ve read dozens of post/answers on F11 and it seems that one of about a half dozen parts can cause it. I’ve done many of the fixes but am now to the point of buying new parts.

My question is.. since the Diagnostic Test does NOT complete and fails at the same point every time, does this tell me what part I should replace first? If it starts at C00, goes to C01 (flow meter/cold water inlet valve), but never displays C02 (Dispenser motor/Dispenser contact), and then goes to F11 (communication error), what is the most likely problem component?

An added clue MAY be that there was a but of “gunk” on top of the rotation point of what I assume is the dispenser (see photo). I cleaned that up but it didn’t seem to help. This may or may not be pertinent, but I thought I should mention it. If I run a normal cycle , the arm moves, noisily, before the failure.

Any thoughts? Thanks for any help.