Sadly, my replacement has also failed in the same way
Basically I've got the InkyPhat plugged into a Pi Zero W, (there's also a camera attached)
power supply: it's plugged into the back of a Sony bluetooth speaker
I've got it standing on it's edge, power lead at the top, so generally the display has been inverted.
Mostly, it's just running a slightly modified version of the weather example that I've dropped in /etc/cron.hourly
I've tested it with various filled solid, and checker board patterns with black, white, and red fills; generally when I've been testing it, the refresh would have been no more than once every 30s
It 'appears' to be the red that fails first; although once it's gone you can't write black pixels to those lines either. Strangely, a solid black fill seems to work regardless, however a red fill will show all of the failed areas.