Thanks for the reply Kenny,

Yes, they were working. I have had this twice. Once from start-up and then once when resuming a different saved flight which hadn't previously had the issue. However, In the dozen or so medium haul flights I have now made it has not occurred since.

I have had problems with my network (I fly with weather provided by AS2012 on a networked PC) and am now wondering if a disconnection from AS followed by a later re-connection may have caused a jump in altimeter pressure setting which might cause this? Just my best guess. Or maybe I missed something?!

As it seems isolated to just those two events I'm not too worried now... it must have been coincidence that they both occurred together when I hadn't long started with the aircraft and made me think it was a larger issue.

Kind regards,

Adam