Foamy fluid is a dead giveaway. For foam to occur there must be air present.

John Quote;

"Stomping the brakes could foam the fluid if you had air and could have also activated the valve in the distribution block that will close one circuit if pressure is much lower on that circuit. It also causes your brake light to come on. These will sometimes reset if left alone over night."

If the air was getting sucked in through the bleeder screws it wouldn't have made it's way all the way up to the MC. Air getting sucked in past a bad piston seal in the MC causes foaming.

Another clue: Quote,"I talked with Vikki and she said she had the same problem with her’s. She said screw it around 1am, and the next day the brakes were ok. Why?"

The answer is a question; What part of a braking system can bleed itself over night? MC

That's describing a master cylinder bypassing intermittently. It can happen just as easily with a new rebuilt as with an old tired one. I have went through three once until I got a good one from the parts store. They frothed up while bench bleeding.