Actually I think the issue resolved itself. Right after I posted this, I went ahead and swapped the suicide battery and later tested the board once more but with a worse display. I felt dread, but tried it on my other A board and it showed a clear picture without error. I tested the other A board again with another game and had no problems either. I may just chalk it up as a bad seating between a+b boards, even though I had them clipped.