I've been working on isolating a few bugs in both SimpleMiniMap and CowTip (both Ace addons), which have been driving me crazy lately, and don't seem to be all that common. At least the authors of those addons don't have any way to reproduce them.
With SimpleMinimap: it crashes every time I try to rescale the window or the minimap. That is, if I change the minimap scale to 0.8, or if I switch from fullscreen to windowed mode, the whole MM dies - all I get is the frame, but it's seethrough.
With CowTip: every so often, the lower-right corner of my tooltip gets set to just about the lower-right of the screen (far right, about 20% up from the bottom). This can be bad, as my original tooltip location was top-left, so it meant my tooltip got stretched all over the entire screen.
Both bugs stopped occurring when I just turned off gatherer in the addons menu. I've no real clue here, but I wonder if the heat-trace HUD thing is messing up the various strata that these other addons interact with. Perhaps those addons do something like reference the strata by number and the HUD creates a new one that doesn't behave as expected? That's just a guess though.
I'm happy to do more isolation testing, post screenshots, etc.
I had also deleted Mobile Frames, because it was causing some issues with my pet training frame, and it turns out: Mobile Frames was the culprit.
Serves me right for using such an ancient hack of an addon, but I really like to be able to drag my character frame around, and nothing else really works (move anything is nowhere near as user-friendly).