ORIGINAL: mobow
Have you retuned your bow since the switch? Changing arrows will change the way the bow shoots, so it may be a tuning issue. It may also be a vane clearance issue, or....more likely, you're torquing the bow more on some shots than others.
That was my initial thought when I read it. The fact that some of the arrows are tailing, and some are not (assuming all else is equal, arrow weight, length, etc).