@Daniele Thanks for sharing your knowledge.
I still use the bootloader that is installed in China, so not the issue for me. I also specify node ID in the sketch to avoid issues with getting it assigned from the GW.
I have had a much better experience lately with new quality power supply, but still had a weird crash this week.
I woke to find the pi running, activity light flashing as it normally does, but no web page served, no ssh access and no activity light on the SSD.
Within a few days I will re-build removing as many dupont connectors as I can and soldering wires instead. It's really the last thing I can think of, but I am seeing things improve which is a good thing! π