HP 41CX Annunciators Become Visible with Long Inputs

[brouhaha]

In my opinion, there's not a lot of reason to swap the logic board. I don't see any way in whcih a defective logic board could cause your display issue. The logic board doesn't drive the display segments. The serial data bus (phase 1 and phase 2 clocks, SYNC, ISA, DATA), power, ground, and a few other signals (e.g. DPWO) go to the display, and the two chips mounted on the display hybrid are the only things that connect to the LCD segments. That's why I previously thought you were talking about swapping the components of the LCD assembly, which could reveal whether the problem is on the driver PCB or the compression connector.