I think being overloaded may explain the problem, at least to some extent.
After the writing the post above, I disabled all of the apps I do not use regularly, leaving only the 3-4 that I find essential.
The situation seems to have improved since then, with the FreedomBox being unavailable once a week instead of three-four times a week.
Is there a log file or somewhere in Cockpit I can check to see if the hardware is overloaded? Same question for the update issue you mention?