Vermintide 2 does seem to be especially susceptible to this issue, so I’m open to the idea that it could be a problem on our end - I’m certainly not ruling it out. I’ll leave that to our brainy developers to decide on though!
I’m equally disheartened that none of the solutions you’ve attempted have worked for you and I apologise that we’re not able to offer more help right now. It really is a case of simply not knowing enough about it.