After experiencing the time jump problem I tested all the boards for stability.
There are two tests, compiling and memtester.
The first is compiling a project repeatedly for 24 hours. An endless loop of make && make clean.
The second test is memtester. I ran it for 20 passes for either 1.6GB or 2.6GB.
sudo memtester 1600m 20
Both Manjaro Phosh and Arch Linux ARM come with multiple u-boot bootloaders that let you change the RAM interface speed. I tested at the highest 624MHz and worked down to slower speeds if there were errors.
3 of the boards time travel. This seems to be a side effect of the RAM speed. For the affected boards the higher the RAM speed the more often the time jumps.
The Ubports upgrade board can not complete a boot cycle at 624MHz. It will time travel at 492MHz when the CPU is loaded.
The Postmarket OS board is stable at 492MHz, with just an occasional rcu error.
The Mobian 2GB board is mostly stable at 492MHz. It rarely time travels.
The rest of the boards are stable at 624MHz. I ran one for a full week compiling continuously.