It sounds to me like you may have a combination of problems. I would go through tuning from square 1.
The other questions I wonder about are:

Are u using helical fletching? Are u lining up the vanes w/ the blades of your bh?
Are the arrow straight? It seems to me the straightness tolerance on Excel's is .600. That's not the straightest.
Do you have rest contact? Do a powder test.
If your walk back tuning is o.k. and you have some minor contact,it won't show up in fp's but will in bh's.
Montec's are not as accurate as some other bh's. Did u see the video in yesterday's post here?