You could try and swap cylinder from one side to other and same with check valves.
i know you mentioned you replaced them, you didn’t mention year, I’m not super familiar with the a7 but the older ones had same setup as the m5000, aluminum block above arm pull check ball valve and make sure it doesn’t have crap holding it open. Only other thing I can think is the actual block above broom arm has a crack, or you have power back feeding to locking valve