But damn, can finding the cause of this be that difficult.
Not offering any excuses but finding the cause for something like this can be extremely difficult. Not so much if the problem is purely in the firmware (e.g., display timing issues) but if it's electrical interference all bets are off. These OLED displays are susceptible to noise and the datasheets for the displays and the display controller chips mention this multiple times. Finding out if this is a problem in any particular board design or installation can be a nightmare though. There are so many combinations of wiring, switch types, current flow, etc., for all the mods it can be hard to spot a pattern that might help to determine the cause of the problems.
If mods like the Hana are having problems then it should be somewhat easier to figure out. They're all the same so even though they're used by different people the susceptibility/immunity testing (electrical noise, spikes, surges, static discharges, nearby radio emissions, etc,) and beta testing should have brought these problems to the surface early on.
I don't know if companies like Hana do susceptibility/immunity testing though. It's a brutal, very fast paced market and this testing takes time and money. I can easily see them depending on Evolv to do this testing and update the boards when necessary to make them robust enough. Trouble is, Evolv can't do this kind of testing for every mod that might use the board.
Not trying to put down Hana or Evolv. I think this is just where the market has pushed everyone in order to be competitive.
[edit] If swapping out the screens fixes all the problems then it's just a bad batch of screens. That can be crazy hard to track down too though. Manufacturers need to assume, for the most part, that the components they use in their designs will work as specified. You can design around some possible component issues but that gets ridiculous after a while.
Tracking down something like a faulty screen problem can be a nightmare because it can appear like any number of other problems: electrical intereference, firmware issues like incorrect powerup/down of the display (a surprisingly complex sequence) and timing of the display data and command transmissions, unstable or oscillating voltages on the circuit board due to unstable regulator, voltage (power) to the display being too low or high, etc. Any of these can mimic the look of a faulty screen.