⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

I want to use my own Nextcloud instance to create back-ups of my laptop. However whenever I try to add another Sync Folder, Nextcloud keeps crashing. The only way to stop this is to edit the nextcloud.cfg file in C:\Users\user\AppData\Roaming\Nextcloud : remove everything that starts with 0\FoldersWithPlaceholders\2.
I tried removing the default Nextcloud sync folder because it kept saying the root of any new sync folder I make is already being synced (duhh, but how can one had a second sync folder then?), but that also didn't work. It still keeps crashing every time I launch the app. These back-ups on my own local server were the main reason I even started using Nextcloud... But it doesn't really seem to work at all.

Steps to reproduce

1. Add a new Sync Folder
   
2. Selecting a folder to add as Sync Folder
   
3. Choosing a folder to sync it to and click "Next"
   (Translation of yellow box: Warning: you're already syncing / , that's the root folder of /Photos
   
4. Click "Add Sync Folder" on the next pop-up
   

It will now open the Settings screen again and show "Nextcloud" default sync folder, and a new folder called "Photos" underneath it, with the status "Waiting...". A few seconds later, it crashes.

Expected behavior

When getting sent back to the settings screen, I expect it to start syncing the folder instead of crashing. And even if it did crash, be able to launch again without immediately crashing. I was planning on sharing my nextcloud instance with family and friends but if this happened to them, they wouldn't know what to do, especially since the app doesn't give any error at all and immediately crashes again when re-launching.

Which files are affected by this bug

All files? Nothing is getting deleted or added though

Operating system

Windows

Which version of the operating system you are running.

Windows 11

Package

Other

Nextcloud Server version

25.0.3

Nextcloud Desktop Client version

3.6.6stable-Win64 (build 20230119)

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Enabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No logs about this issue (yes im sure, there's only login logs)

Additional info

No response