I found a bug, that lead to out of sync multitrack playback. At first it was on a gig (yeah, I am testing BETA at work). Some of the songs were playing slightly out of sync right from the start, maybe some tracks in a song started with a slight delay, not all together. Not a big drift, but enough to start a panic attack. It happened 3 or 4 times during 2 days of testing. These songs were playing 100% perfect before. If stopped and started again - all perfect (didn't tried at a gig though).
I made a full backup of the latest stable version and imported in beta yesterday. Same hardware as before (iPad Pro 10.5+powered USB Hub+UMC404HD - 3 months playing with this setup, 6 days a week). At home I installed latest beta 8861 and still managed to reproduce this issue even without audio interface, just with the built in speakers.
So what I found is when you select a new song (all are 6 track multitracks) and select last region, for example, Press Play - all tracks were out of sync. Stop->Start again from the same region and all perfect. Next song -> Select last region->Play - out of sync. It happens not in every case, but very often. I can record a video. Even if I wait for couple seconds after selecting a song. Obviously at work I start all songs from 00:00, but for the testing purposes I selected the last region in every song and press Play.
6 tracks mp3 320kb/sec, 44.1kHz, 2048 Buffer, no pitch or speed applied.
Just tested the same songs all over again in the latest stable version (3.7.5) - all perfect, even if I select songs and regions really fast (I thought maybe it was a loading buffer issue).