"I do not use sync and do not adjust grids" -- and that could actually be the key.
If you have analysed the songs in DYNAMIC mode, but they're all perfectly consistent tempo tracks, the system is working to try and warp the tempo up and down as it plays the track, regardless of sync. Any electronic-percussion songs should be analysed in NORMAL mode to avoid this issue.
Please try re-analysing a few tracks which you have noticed to be problematic and see if this resolves it for you.