Keep having to reload synths

I have occasionally had this issue in the past but now it's happening every few minutes.
eg working in PRV with GPO loaded and moving notes around and then all of a sudden no sound. 
It shows midi activity in inspector during PRV playback and when hitting a note on Axiom 61.
I simply reload the patch in the synth UI (in this case Aria but has happened in Rapture etc) and all is well...for a few minutes at least.
Any idea what could be causing this?
Thanks very much,
Randy

BTW there is only 1 track at the moment and input echo is set to auto 
EDIT 1 I now have 5 instances and they can all go silent at once and have to reload each one individually to get them back
EDIT 2 crap even my metronome click disappears and I don't even know how to reload that
Is this a unique issue?