Steve, I've never seen OLED's present this way. They usually show up with pixels scrambled, or every other row of pixels off, but I've never seen a stripe through them, or half a box created. 

The error message in your picture is simply the adafruit library not able to find the OLED's at all.

My best suggestion would be to test each OLED by itself, without the multiplexer (you can use the test script for this, just be sure to change the number of OLED's in settings to 1). If it works with the test script then try it with the main program. Then repeat for the other 4 OLED's to ensure they all work. If so, the problem may be in the multiplexer or wiring. - Mark

Well the horizontal line that appears in the photo is about the camera refresh rate... There isn't really a row missing... But as often, one OLED simply doesn't appear or partially appears and they freeze. The OLEDs stop changing and the error sequences recur. I've tested each one and all wiring is fine. 

Well that makes sense about the camera.

The LiveSectional software has nothing to do with the error you are receiving. As mentioned, the Adafruit library used to control the OLED's is not finding what it needs and then quits with an error. If you know that all the wiring is correct, maybe its one of the OLED's giving you fits. Does it quit on the same OLED each time? - Mark

Frustratingly, no. It cycles 1-5 for a while then goes to the errors I showed... Then just now it resumed working for a few minutes, showed the error and still appeared to scroll through screens a bit... Then the OLEDs stopped scrolling and locked-up again. Sometimes I have to remove power from the multiplexer and the OLEDs, so that we can get it working (temporarily) again...

Then I would suggest replacing the multiplexer. It seems to be the only common thing given all you have described. - Mark

I bought a 2-pack and tested with both... and also switched to solid wire from the Pi to the multiplexer. No consistent joy. Sometimes I will get random "static"-looking pixels on the displays. Sometimes nothing. I wonder if I need to do a solid-wire for the 3.3V, maybe?

Is there any chance that 2 instances of metar-v4.py is running at the same time? This can cause the issues your describing. - Mark

Posted by: @markyharris

Is there any chance that 2 instances of metar-v4.py is running at the same time? This can cause the issues your describing. - Mark

I wouldn't think that possible... I just used your image, un-messed-with.

It's possible to have multiple instances running. One of the easiest ways to do it is to have 'Autorun' on and then going to the 'Map Functions' menu and selecting 'Turn On Map'. This would run the program twice which would then fight for the LED's and cause issues similar to what you described. It's just a thought. - Mark

I'm leaving a note here (and other help threads where I've been frustrated) in case it helps someone. I re-did all of the electronics and now appear to have solid reliability and consistent operation. I strongly believe that the basic jumper set had very poor crimped connections and this made for some intermittent and weak connections. I shortened all wire runs and used solid core wire for many components. For those situations where using the jumpers remained beneficial, I took off the black shielding with a needle and touched a tiny bit of solder to each wire connection and replaced the shielding. Any connection that didn't FEEL solid, got a light squeeze with a crimper before pressing onto the terminal. I also had an unnecessarily-long run for the LED data line, and this seemed to create a host of issues. Shortened and tightened and all appears well! Bottom line, TIGHT and short connections are very necessary for a bulletproof project.