Thanks for the reply Windell. I think actually the green ring working was my imagination as I put it straight in to alignment mode and didn’t pay that much attention.
I’ve desoldered/removed the red ring and it still shows the same problem:
It starts in reverse and the transition isn’t smooth – the two LEDs flicking between them at full brightness during this and I’ve noticed the green (and red when it was still attached) have whatever LED is lit flicker at the same rate likewise.
What has changed is though by virtue of how I was holding the base PCB my thumb brushed across the external/USB-TT connector. The clock reset back to 12 and whilst still running backwards, the transition was now smooth. I can recreate this over and over – it starts/boots backwards with the problem, touch the connector so it resets and it then works fine (but backwards). Once it’s running correctly I can then alter it to run the right way. It seems to keep the time well in all conditions too.
I’m stumped. Maybe the ATmega didn’t take the code properly – just one character stored incorrectly causing the random problems?! I might have to give up on this one I think.