Video switch stops working in flight

After a few minutes of flight the video switch stopped working. I was lucky because I was on the front cam, but if I wasn't I'd probably crash my wing in the woods. The OSD was working normally, all information was displayed, only the switch suddenly was dead. Any ideas why this happened and how this can be avoided?
The OSD is hooked on HKPilot mega mini powered with a dedicated 3A UBEC
The front cam is:
http://www.surveilzone.com/0.0 ... c1564
The rear cam:
http://www.banggood.com/600TVL ... .html