Hello. I identified this issue way back and after some research and testing I contacted SS support about the “red line” at the very end of the last bar on a beat or a fill. This is supposed to indicate that there’s hidden information past the last bar which will overlap with the following beat -like when you need to add a crash starting the next beat but not include it in the beat itself (so that it doesn’t repeat as it loops!)
The red line always appears on imported beats/fills but it also exists already on some SS content EVEN when there’s no info in the next bar (a bug). This causes missing or overlapping the very first note on the next beat -I don’t know why the miss…
So, the quickest way to solve this is to open the beat/fill on the BBManager, to edit, see if there’s a red line and, if so, ADD one bar and REMOVE it immediately. Hit Apply and try it.
I hope this helps -until the new BBManager/Editor makes its entrance… sometime… in a not too far away future.