[popcornmix]

Running overclocked mode. Can test more tomorrow: what do you suggest: test with 'older' build or remove overclock?

Jonathan says the mask=2 contains most of the complicated code, so removing that bit is most likely to avoid the problem (but also avoid most of the benefit).
The mask=0 failure is more surprising.

Perhaps remove overclock, and check mask=0 case a few times. Try to confirm if it is consistently worse than mask=1 or mask=4 (I'd predict it to be the same).