I'm not familiar with the Denon controls, but is there any chance you are adjusting the "rear" (speakers 6 and 7, ie only in a 7.1 system) levels rather than the "surround" or "side" (speakers 4 and 5 in a 5.1 system) levels ?

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