IIRC, one little-known hack to get perfectly synced loops on the SX and A was like this:
Say you have two samples, both are labelled as eg. 120bpm, but they obviously aren’t both exactly 120, b/c they go out of sync. Well, press TIME/BPM button (I think on the MK2 this has become PITCH/SPEED, in combination with the correct setting to only affect tempo, ie not vinyl mode) and use the appropriate knob to change the bpm value, but then change it back to 120. You have to change it back to 120 manually with the knob to the correct position, not by removing the bpm edit (which would be done by either turning the knob all the way to the left, or I think pressing TIME/BPM again so it’s unlit—either of these undoes the edit and reverts to the inexact “120bpm” again). This has the effect of editing it to exactly 120bpm. Then repeat this process for any other sample you want at that exact TIME/BPM value…
Okay, having written all that, I have no idea if you can implement this hack in the MK2 since clearly the whole data structure is different/more complex, but there it is. I might be misremembering this hack; hopefully not.
BTW I know I’ve gotten loops to be in sync enough (like, for minutes straight, certainly 10s of reps) on the SX even without this hack, just with some trial and error fine adjustment of START/END.
Edited for clarity.