Yep. I have noticed all that as well. His positions are all over the place as he plays role of opportunist — making comments that get him airplay then explaining them more later. Familiar pattern. But in this case it was a pretty lame question — should be there be punishment for breaking the law? Of course. What is he supposed to say?
Exactly what you said. Not what he said -- a lame answer to a lame question.
The problem appears can be summarized as "running your mouth without any serious aforethought" -- something that a Republican candidate simply can't afford to do. You might say that Trump suffers from Todd Akin Disease...