Sony FX1. I use the viewfinder most of the time.
Whilst filming - it may also occur while I'm on standby - suddenly the colour bars pop up. When it first happened - right in the middle of a shoot - I had to switch off the cam and switch it back on again.
Today it happened again - I opened up the viewer screen, pressed the 'Bars' button, closed the screen and was able to continue filming without losing too much.
But, as Mr Sod will testify, it invariably happens at a crucial part of a shoot: today's was a sporting event. No retakes. What is lost is lost.

Any ideas as to why this is happening, and more pertently, how I can prevent it from happening?