I've done some additional testing with a fresh install (no backed up ini) and I seem to have located the problem.
PiP switching seems to have broken across monitors, I'm running 2 monitors, 1 with my main and 1 with my 4 slaves, when I'm over on the slaves monitor I can switch between them without any problems, but when I'm on my main I cannot switch to any of the slaves.
I downloaded and retested it with 1.9g and it still works fine there