No results yet, but they asked for an app to better reproduce the problem, and I'm trying to put something together for them. It's sort of difficult as at the moment I can not see the effect here at all - there's something random to it. It only happened on two machines that both had the 169 drivers, so I assumed the driver was the reason.

I will continue until the problem is resolved or at least the reason is definitely determined. When there's something new I'll post it here.