Comment 5 for bug 1539009

OK, so sounds like a Mir bug, but a Mir bug that only Unity8 would ever hit. Because the bug would only happen in clients (or nested servers) who use the relative motion data instead of the usual absolute motion data.

We're only delivering one relative motion event to Unity8 every 17ms (59Hz as intended). Therefore on your normal 125Hz mouse we're dropping 50% of the motion information. And on my 1000Hz mouse we're missing 94% of the motion data.

It's a solid theory that explains everything we've seen.