It could also be a "procedure" problem.
When bleeding - "DON'T PUMP THE PEDAL."
Pumping turns the air pocket into foam, nearly impossible to get out.
You think you got it all, but in a few minutes, once the foam turns back into an air pocket - low pedal again.
Just have your helper "Push Steady," open, close, "up", then Push steady" again.
You can still do the bench bleed procedure after it's installed, it's just harder to do.
If you got the MC from AutoChina then it may be bad - I've had very poor results from them! The only thing I'll buy from them is packaged name brand chemicals - even then, they play the "bait and switch game." What they advertise isn't what they ring up - you have to fight with them every time.