I have been having the same issue since installing latest 11 update. Any virtual instrument i use, the output goes crazy after a while. For instance, i will use kontact player 6 (updated) and lower the main output to about - 6 db. After a while it jumps to 0 and you can see it jumping non stop. Trying to lower it back to - 6 does nothing. Just jumps back to 0. This happens on any V. I. track i use. Any info be great .
Ty, Vin
It may seem a silly question but have you accidentally enabled automation on the track? Do you see the slider actually move up and down? If not have you drawn levels on the actual parts?
It is quite easy to accidentally record automation or forget you did it. I know I have. If not one of the above then I’m not sure unless you have recorded a cc7 or other cc into the midi data which would/could also change volume.