It sounds like fall-off zone problems,IMO.  Philc is the master of fall-off zone problems.  If the inner or outer mat zones are off you'll have problems just exactly as you describe. You ought to check out his tutorials.

I cannot save the world. Only my little piece of it. If we all act together, we can save the world.--Nelson Mandela
An  inconsistent hobgoblin is the fool of little minds
Taking "Just do it" to a whole new level!