I fixed the problem.
I uninstalled the GOG software and then reinstalled it.
It didn't recognize BG3. Before manually specifying the game folder, I deleted the contents of the “Launcher” folder in BG3.
I went back to the GOG Launcher and manually located the game folder.
It automatically started the update/verification process, and after that, everything worked normally.
Previous attempts to “Check/Repair” were unsuccessful.
It’s probably enough to just delete the contents of the “Launcher” folder and run verify/ repair.
VSync problem is under bg3.exe which is Vulkan.
DX_11 works normal.
