I am trying to connect an analogue source (Rega P2 turntable connected to an Audible Illusions Modulus 3 pre-amp+phono-stage) to my 808.3 and have encountered a strange behavior. The 808.3 has 6 sets of stereo analogue RCA inputs and when I connect to any of the side-by-side inputs (e.g. A1 and B1) I get only one channel. But when I connect them to jacks on on top of another (e.g. A1 and A2) I get both the channels. Is this expected behavior?

I have tried to rule out a typing error by changing from my custom type to the standard type 1 and there's no change in this behavior (it is consistent and replicable). All other inputs work fine (they are digital). Any thoughts would be greatly appreciated

Sources: Roon Nucleus, Oppo BDP-103, AppleTV, Processor: Meridian 808.3 , Speakers: DSP7200SE, Projector: SIM2 Lumis, Stewart 140" Custom Filmscreen