[Bug]: E2EE encryption of folder fails with "The folder has a minor sync problem. (...)"

### ⚠️ Before submitting, please verify the following: ⚠️

- [x] This is a **bug**, not a question or a configuration issue.
- [x] This issue is **not** already reported on Github (I've searched it).
- [x] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/)

### Bug description

When I try to encrypt (E2EE) a folder in the desktop client via right-clicking it and selecting "Encrypt" in the context menu nothing happens. Instead I only get a pop-up window saying "The folder has a minor sync problem. Encryption of this folder will be possible once it has synced successfully".

The synchronization actually seems to work flawlessly.

The client says that E2EE is activated for the account in the green banner at the top.

The folder I want to encrypt is located in the root folder and is empty.

### Steps to reproduce

1. Right click on the folder on the desktop-client
2. Select "Encrypt"

### Expected behavior

Folder should be encrypted.

### Which files are affected by this bug

zzzenctest (folder)

### Operating system

Windows

### Which version of the operating system you are running.

Windows 11 Pro x64 24H2
Build 26100.3037
Windows Feature Experience Pack 1000.26100.48.0

### Nextcloud Server version

Nextcloud Hub 8 (29.0.9)

### Nextcloud Desktop Client version

3.15.3

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

I have not tried E2EE before, so I can't say.

### Are you using the Nextcloud Server Encryption module?

Server-side encryption is disabled.

### Are you using an external user-backend?

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

### Nextcloud Server logs

```shell
Unfortunately I cannot provide a logfile of the server, as I do not have access to it.
```

### Additional info

I already unsuccessfully
- tried resetting the end-to-end encryption settings on the server via the webinterface under "Personal -> Security".
- de- and reinstalled the end-to-end encryption app on the server. The version of the E2EE app on the server is 1.15.2.
- forced the synchronization