Joe, I can't speak to the shoe adjustment on the fronts but the rears were up plenty tight enough, adjusted them myself. System acts as if there is a leak. Could be a "mouse" in a hose but I didn't notice anything odd last night when we were working on it. Would explain the sudden system change. Everything else appeared clean & dry. I agree. Time to start with a clean slate. Double check all four corners including WCs and shoe adjustment. Double check hard lines and hoses under pressure. (what little we can muster at this point) If nothing odd is found then I suspect we either got a bad MC, as Jim states it does happen, or we got a MC without check valves. To check this, my MC is currently setting on the bench waiting for me to finish installing the new brake lines. This is a known good part from a similar system. We could install it and eliminate the MC as a variable in the equation.
I talked with a couple other people today about this problem. This short list of solutions is about all there is. The system just isn't that complicated. That said, I've never experienced this much trouble bleeding a brake system; any system!