There is a bug in the Voltage Processors Mod input for channel 7-8. When mod in is used, then it will not output channel 8.
Also i find all the mod ins to be reversed. If we say uneven channels are left and even right, then it would be logic if a negative/ left mod amount went to the left/ uneven channel, and a positive/ right mod amount went to the right/ even channel, but it works the other way around.
Both the bug and the reversed behavior is the same in ARP 2600 V2, so this has'nt been rebuild or checked and fixed.