I'm getting a similar issue with my hihats jumping across my speakers when I play an open note, although I'm using xy. I've heard the phasey sound in cymbals can be a common problem in glenn johns type techniques when a mic is facing an edge of a cymbal rather than most facing the top of it. Maybe see if the mic is angled to face the edges of the cymbals when they move when being played? I can't think of anything else than that.
Overall it sounds good, but I see what you mean about the drifting thing.