I work with a ton of Datapaths and have come across two failed units that continually flash. In my experience when they fail in this way, you can open the control software and see the input frequency changing constantly. I had one just the other day reporting 3840x1080 @ 520,000 hz!

Not sure if that's your specific issue as you say it doesn't happen all the time, but if you connect a pc with control software you can find out pretty quick.

-Phil