I have a UBP x700, and haven't had any issues with the Doobies or Chicago, etc... I know I did see some folks talking about how to muck around with settings (I think
@GOS gave me some pointers if I'm not mistaken), and this may not be news to you but I didn't realize to what degree I could play with settings on the UBP itself (going to the Settings menu from the UBP home screen, up in the top right). Being able to select whether the UBP defaults to 2ch or multi, etc.—might potentially be a quick fix in there, but again, you may know this stuff already so my apologies if it's not helpful!