I have now found what I believe was my problem with print problems following firmware updates. In short my problem appears to have nothing to do with the firmware.
With 1.1.4.8 I had ~3 successful prints before I started getting a system error when printer was just starting to print the second layer. I tried restarting multiple times but it kept stopping. Going back to 1.1.3.,13 all was OK.
When 1.1.5.5 arrived I managed to get several dozen successful prints before it started stopping again at the second layer. Sometimes no error message - printer would just hang, or report nozzle not heating. But this time I also the same behaviour when I back graded to 1.1.3.13.
I then sat down and looked at what filament type I was printing with . It turns out all my successful prints were with non-PLA Silk filaments and all failures were with PLA Silk (don’t normally print much with this filament type). I then checked the PLA Silk filament settings and WHALA! one of the ~3 settings had the nozzle print temperature for second and subsequent layer at 22ºC instead of 220.
So it appears all was going along OK till I decided to print with PLA silk with that specific filament setting and this is why it never got past the second layer. I am surprised that such a ridiculously low second and subsequent layer temperature is not flagged by Creality Print before saving filament settings.
I would also have spotted this earlier had I tested with the exact same parameters following each firmware update.
Live and learn.