few reasons why this could be happening
- Engine Prime calculating a wrong BPM
Workaround - Inspect BPM on EP and type in the right one before exporting if you analyse in EP
Alternate Workaround - Disable EP autoanalysis, export tracks sans analysis to Prime 4 drive and let Prime 4 analyse the tracks (this happens when you load the track), Prime 4’s most recent firmware allows it to use BPMs in tracks metadata as a guide for its bpm analysis. Same feature is expected in EP software and other Prime devices at he next update. Ensure you have info written to tags in Traktor, so the tracks ID tags contain BPM values following analysis in Traktor.
- Engine Prime calculating the correct BPM but not detecting the downbeat correctly. All softwares have this issue, some are better at detecting the downbeat though eg Traktor (but doesnt have flexible beatgrids)
Fix - Slide the grid right or left. You can do this mid gig or whilst managing your library