After upgrade to 34.0.1 disk usage spikes, resulting in out of space messages

Last week I updated my home nextcloud installation and all went well, so great

However I started getting e-mail from my system (and I thought this had to do with me fixing the e-mail, but that turned out to be wrong).

The e-mails contain things like:

PHP Notice:  fwrite(): Write of 425 bytes failed with errno=28 No space left on device in /var/www/nextcloud/lib/private/Log/File.php on line 56
PHP Notice:  fwrite(): Write of 425 bytes failed with errno=28 No space left on device in /var/www/nextcloud/lib/private/Log/File.php on line 56

The log directory isn’t set, so it is writing in /var/www/nextcloud, which is on the /var partition. When I look there, there’s 17GB free, so what’s the problem I thought…

Since the upgrade the storage varies by so much, that it becomes full and then empties again. That is a lot!

I’m guessing something changed with the backup, but the release notes for 33->34 are empty?

Can anyone shed some light on this?

Not unless you provide the context requested in the support template which you seem to have overlooked.