Sorry! The other post I saw asking about it didn’t seem to follow the template so I assumed it wasn’t always necessary, my mistake. I’m very new to all of this and there’s quite a few bits of the template I’m unsure of, but I’ve filled it out below as best I can. There are some logs I’m not able to access right now due to my location and extremely limited grasp of linux (currently away from the host system and unsure how to SSH in from here), but I’ve tried to answer everything I can and hopefully it’s still of some use, but if not I’ll follow up with the remaining logs as soon as I can get to them.
Support intro
Sorry to hear you’re facing problems 
help.nextcloud.com is for home/non-enterprise users. If you’re running a business, paid support can be accessed via portal.nextcloud.com where we can ensure your business keeps running smoothly.
In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 29.0.5): Nextcloud Hub 9 30.0.0
Operating system and version (eg, Ubuntu 24.04): Pi OS Bookworm (Debian 12) / Linux 6.6.51+rpt-rpi-2712 aarch64
Apache or nginx version (eg, Apache 2.4.25): Unsure, but if it helps at all I’m running it through a Cloudflare tunnel
PHP version (eg, 8.3): 8.2.23
Calendar version: 5.0.0
The issue you are facing:
Is this the first time you’ve seen this error? (Y/N): Y
Steps to replicate it:
- Make multiple calendars in Calendar app
- Try to rearrange them
The output of your Nextcloud log in Admin > Logging:
Text was apparently too long for both this box and pastebin so I've uploaded a notepad file of it here:
https://mega.nz/file/HV5x0BKL#_eFmS-3bBKjiwB9TjB6NhxzGMsB6hO-xrI0oFsW2Tgs
The output of your config.php file in /path/to/nextcloud
(make sure you remove any identifiable information!):
PASTE HERE
The output of your Apache/nginx/system log in /var/log/____
:
PASTE HERE
Output errors in nextcloud.log in /var/www/ or as admin user in top right menu, filtering for errors. Use a pastebin service if necessary.
PASTE HERE
Sorry again for my ignorance on this in general and the lack of some stuff requested, no worries if you can’t help from this limited info I appreciate there’s a lot missing.