Apparently it was an issue with Pi devices to:
"Or if the clock is being kept to frequency by a PLL, and the PLL has wider tolerances than some HDMI devices like, it may be that it is drifting a little too much? (I think this was the issue with the Pi / Pi 2 and AVRs where we were getting black flashes, and a config parameter allowed you to reduce the amount by which the HDMI clock could drift? The drift was intentional to allow for small video or audio timing errors to be corrected without dropping / repeating frames?):
… more here: https://forum.odroid.com/viewtopic.php?t=11837&start=100