Just to update this. I just caught sight of my processor activity when this happened again and indeed there is a 100% spike in one of the 8 processors on the slave.
Oh and I just saw it happen again and the sequencer is not playing in fact both machines are idle.
So for about half a second my processor read out looks like this:
100% 8% 1% 3% 7% 11% 10% 6%
Then the one at 100% returns to normal.
When looking at the Activity monitor I can see that VEP is sitting at around 35% (even though the little read out in VEP says about 4% ......why such a difference I wonder)
When the spike happens the Activity Monitor read out for VEP goes up to 100% and the sound from Kontakt stops.
The next thing I will try is turning off multithreading in VEP.