Brakes locking up

I had that issue long ago, because the pushrod to the master cyl was too long. My fault, turned it in at the threaded adjuster back about 1 1/2 turns. There's a way to measure, in the FSM. Bad brake hose can do it also. The distribution block is brass, not much to corrode inside; although old fluid could carry some rust deposits there I suppose.
I think there's a more likely answer.