Hi Jospoortvliet,
Thanks for your interest.
This is my issue, and others as far as I can tell?:
I tried to follow recommendations from this support forum but couldn’t get that to work, adding a line to my php.ini as instructed just ended up crashing the server.
I hear what you are saying, of course, Nextcloud is great if you are experienced in all things php and great at setting up servers and all the ins and outs and pitfalls of this. Some of us however are not so good at this and require assistance. This is what I thought the forum was for.
I would like to submit a good bug report, really I would, but I totally failed to manage to provide the information requested. I was not even able to provide a copy of the relevant files because I couldn’t figure out how to copy and paste from the command line to provide copies of the requested files That is how dumb I am 
So, it could be said, natural selection has taken it’s toll here and I should not be left alone with a complex bit of software such as Nextcloud and a Linux server in general but, guess what, I enjoy this, I managed to get it up and running with lots of help from kind people on forums, just like this one, and I have been successfully running my own little NC instance since version 14 or thereabouts. So, forgive me for thinking that something was wrong with the upgrade when I have had so many successful ones? in the past, major updates as well as intermediate ones and now, suddenly, I click on the web updater, coax it along while it fumbles and drops the downloads continually before finally achieving a successful update only to find that, around 15minutes later, my server is frozen. I finally managed to get ssh access and run HTOP and see that the resources are maxed out by my cron job.
And there ladies and gentlemen is where my knowledge runs out and I turn to the forum.
So, I will try jumping over V21 and on to 22…stranger things have happened, who knows, it may work.
thanks for your insights, I do appreciate that we cannot hold up progress due to an insignificant few, i.e. not a significant percentage of the 200K servers out there! and I apologise for my lack of experience. NO doubt I will improve over time as I work my way through the issues.
James:
P.S.:
I finally solved the issue, well, it may have been partially solved by the NC21.04 update also?
See this post for my eventual fix: