Im sorry about your issues. Im not sure it would help, but worth a shot after you try everything else (swap wires, check post)... is to reset the unit, and leave it unplugged from socket for a decent amount of time. then try again.
Also, though I am sure you are 100x more familiar with your speakers than I am, often the better speakers up the line in any brand (and yours are such: better/best of BA), the loads are often more difficult to drive. I think they allow lower impedances for punchier bass, at least sometimes. fwiw, some midline B&Ws and Focals, though rated nominal 8 ohms, do in fact drop to 3.0 ohms. Yours have a good sensitivity. But so do mine, yet the load can still be very, very difficult.
Just fwiw. If you didn't have problems before, then it sure is strange. good luck.