I noticed you switching between 100 and 125 grain heads..........

I'm far from a technoid when it comes to archery (Haven't changed my setup in 4+ years), but, I did find that going from a 100gr montec to a 125gr montec on my CX 300's caused some "roll". My guess is the add'l weight decreased the effective spine of the arrow. The 100's fly like darts to this day.

I guess when you are at the edges of the "spine charts" little changes can make dramatic differences.