Harry,
Thank you again for your reply.
Yes I do have hardware on the bench. When removed from the hardware the effect is the same, with a low reading. The simulation with the 1k replaced by an open circuit still says around 2.5V.
I could try buffering the inputs before they go into the amps, but I'm confused as to why the Sim didn't respond to this imbalance.
Would this account for the error of approximately 0.54V?
Thanks,
Matt