I don't know much about the TRS bridges, but did you have to also dowel and redrill the mounts for the posts?
If so, check them for play. If they are coming loose that can cause this type of instability and PERHAPS the heavier
gauge strings simply brought out a problem that wasn't showing up with the lighter strings.
Go to ibanezrules.com and go through Rich's tuning problem checklist, it's very comprehensive and may help you find the problem, I can't tell you any more than his site can.
Mic