[dbavirt]

My original test was with single setlist, multiple songs, not grouping all tracks into one list for playback.  I just tried grouping all tracks and the issue is the same when I switch between tracks within the player, same song.  The first few are immediate, then it bogs down, and I can see in task manager that mobilesheets is using 85%+ CPU consistently whether the track is playing or not.  So it does not appear to be related to switching songs/set lists.

I'm trying to replicate on my desktop now.

EDIT: I'm having similar problems on my desktop, Windows 10.  The MobileSheets app starts using 100% CPU.  I'm not able to replicate it fully, though, because of other problems, below. 

* I was not able to restore a backup taken on my 2.3.9 Surface Pro 5 on my desktop.  It said it couldn't write the files.  (I've honestly not used MobileSheets much at all on my desktop so I don't have a baseline for "working".)
* When I add songs, and then add audio files to songs, it says "Unable to load file" even though I can see the file in the directory within the library location on disk.
* When I first add the song, before clicking "OK", I'm able to preview it, but after clicking "OK" I can't play it, I get the above problem.

I'm not going to test further on the Surface Pro because it is critical equipment for me tonight, and at least it is displaying songs correctly as before.

The problems on my desktop went away with a recent release.  Seems I was having problems with the new audio engine playing from a non-default storage location.  I was able to restore to desktop from backup, and the problems playing songs went away.  Thanks for resolving these bugs.