Hi, @Portisch, thanks for the advice! 
I’ll try a fresh install of 19.3 today, and I’ll turn logging on from the start.
Three things, though:
- It’s a bit late to ‘not try to upgrade’ as it has already happened.
- I did not have a choice about uninstalling addons, the system did that automatically.
- I will always remove library, file, and network identifying data from logs, they are not required for fault finding. I have detailed the file information, it behooves me not to invent that.
I will try to find appropriate test files from dolby, and then obfuscate network details, though.
OK, more logs edited into the thread on odroid. The key things that appear to resemble the issue were:
A (perhaps uncaught by logs) time where a local test file kept buffering (a coreelec swirling thing).
When I switched the refresh rate to match the screen’s refresh rate, the screen started blinking after playing a blu-ray rip. Lowering that to 23.497 (or whatever it is) stopped that from happening.
That second one was akin to the issue that I saw previously whilst actually playing files, even with the refresh at its lowest (plugged into either TV or AVR).
One question I’ll bring in from the odroid forum:
Is there a way that I can test the power to the device in the OS?
EDIT 1 - Further Troubles and Troubleshooting Enquires
I’ve had more issues, with full uhd Blu-ray rips, remuxes, and still some h.265 1080p content that plays fine on the LG B7 native player won’t run on this more powerful hardware. Which really troubles me. As well were okay before, and they no longer are, and this is a fresh coreelec build on the sdcard.
I’ll continue to try new HDMI routing, I’ve found some thick Amazon, high speed, C3 cables. They’re not certified 48gbps like my favoured ones, but they’re solid 18gbps Amazon, so they should be okay for this.
I’m wondering if there are issues with power of the HDMI timing of circuitry … but I don’t know how or what to test that with.
BTW, I can’t test from a USB3.0 SSD, or emmc, as I don’t have an available option for that. However, I’ve played back high bitrate stuff on this before, even over the gigabit LAN from a mechanical drive on the server pc, and it’s been fine before. I’m not sure what’s holding us back here.
Are there coreelec trouble shooting add-ons, maybe? Maybe for HDMI, or power draw, testing? SdCard degradation?
I am wondering if this is related to the issues that @discODon99 is having here, or that have been discussed in this long thread (which may have seen some progress in 19.3, here.
EDIT 2 - Odroid UK PSU
Is it possible that I’ve got the same barely passable PSU as @flappy81 reported a couple of years back, here?
Could a 1.5A PSU not be able to push enough power to the board to capable do what it needs to do?