I guess I am missing something. It sounds like your question is why are you getting balls grouped together, but I would need more info.
Is your question, why do you get groupings in general, or is the group always right near the rack area?
Are the balls separating and coming back to that area, or are they just staying in the area without much movement?
Where are you breaking from? English? How are you hitting the 1 ball (cut or full)?
Assuming you are making sure balls are touching in the rack and given the 1 ball is ending up in the corner, I am guessing you might be cutting the break a little to much. But, if you did, how is the cueball getting up table.
You really need map out the approximate paths (not just final locations) of the balls during the break to better understand what is going on.
