The OS isn't downgradable - and that includes re-installs (and that's sheer stupidity).
OK, further observation.
It seems like the people who wrote this OS may be incompetent.
With the NAS at rest, the CPU activity cycles from 5% to 99% every few minutes, and the disk light shows an almost constant high level of activity. My guess is that the OS was written for multi-core CPUs and gives appalling race error problems on single core devices rendering them useless.
Unfortunately for reasons of other things going on, unless I can find an alternative solution, this risks becoming an iminent threat to my mental health