In the last few days I've noticed that intermittently the display screen on my transmitter is staying blank when I turn it on, meaning I can't make any adjustments...it only happens every now and again (normally the first time it's switched on from cold) but I'm worried if it happens at the wrong time I'll be screwed.

Has anyone else had this issue? Any ideas what might be causing it?

Voltage is @7.8v so don't think it's flat battery!?