@xeno-x
Did you check the resource usage?
Especially since BDO uses Xigncode3, a heavily intrusive Anti-Cheat that is sorta infamous to be CPU-heavy and not easily removable (you gotta manually mess about in the OS registry to actually get rid of it). I could get into more detail on what undesirable stuff it does but you do you with your software choices.
If you happen to have the Audio run over the same cable as the video signal it might be that your GPU is dying or the driver isn't up-to-date. Might be worthwhile to check on that.
You could also try to use the GX limiters, is only really reasonable if there's some weirdness on the resources side of things is going on tho.