Just as a sanity check, are both SD cards running the same kernel?
The ReefPi 1wire code is pretty boring, in that it only knows how to read devices the kernel provides. Maybe its now reading faster? Only impacting difference I could think of.
Thanks for the suggestion, both seem to be running the same.
Linux raspberrypi 5.4.51-v7+ #1333 SMP Mon Aug 10 16:45:19 BST 2020 armv7l GNU/Linux
Just as I was checking the card with 3.4 it immediately gave the errors but yet to see one on 3.3.1.
