I was not familiar with what that environment variable changes (makes the video updates not wait for the monitor vertical blanking interval); according to some other info I found that is a Mesa environment variable, so will work with the Nouveau driver, but not the proprietary NVidia driver.
That was from two years ago, so no clear if this still applies, but at that time the equivalent for the NVidia binary driver was:
__GL_SYNC_TO_VBLANK=0
Just in case someone else is trying that solution with the close source driver and is not finding success, try the second variable to see if that helps.
On that page someone also added a comment that you may be able to globally disable VSync using nvidia-settings application or tool of some kind, but I did not see a response if that was successful or not (the discussion on that page was around game performance).
at least you got an error. something that’s really bugging me about my mixbus/ava problems is I’m often not getting errors printed to screen. i provided a screenshot to harrison support showing the gtk errors getting printed while everything seemed to be working fine, and then i provided other screenshots that show the graphical bug but with nothing getting printed to the terminal. and mind you, i’m running MB with the --sync option in attempt to debug.
i had another issue a few weeks ago that Robin helped me diagnose. I was trying to export a CD wav with associated toc and/or cue files. the problem in that case was that I was using a musical flat sign in the metadata. but what irked me was that MB printed something to the terminal that pointed me in no direction, while the same action in Ardour explained specifically that the presence of a non-UTF-8 symbol was causing the problem.
i guess i need to let go of my assumption that MB is just Ardour with plugins built into the mixer UI. And im assuming things will only get worse under SSL.