If the problem still happens when Grid is the only thing running, try wiping your Grid saved variables and reconfiguring. If possible, only change a few settings at a time from the defaults and see if you can narrow down what's causing the problem.
This is what I did first, aside from making sure only 1 ranged was enabled. I did an AV with a generic profile/savedvariables and seemed less jittery as far as going in/out of combat. I look at the new SavedVariables and the formatting is different than my old SVs, so I'll reconfigure it and post here with any progress.