If I had to make another guess, I would guess that QS8s on the back wall have few problems with auto-polarity while QS8s on the side walls drive the auto-polarity logic batty...

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8