[Bug]: Nextcloud virtual files cannot sync some files

### ⚠️ 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

I hate to say it, but Nextcloud 3.15 is the worst release ever.

- 3.15.0 When Windows 10 virtual files are synchronized to the local computer, some files cannot be synchronized to the local computer, resulting in a crash. After that, the system will automatically synchronize and crash again without any error message.
- 3.15.1 When Windows 10 + Windows 11 virtual files are synchronized to the local computer, the Nextcloud crashes, which is even more serious than the 3.15.0 version. It is directly unresponsive and stuck.
- No translation files were imported in the 3.15 version release.
- Error message: Multiple accounts are sharing the folder
This configuration is known to lead to data loss and is no longer upported. Please consider removing this folder from the account and adding it again.
Currently, Nextcloud is unavailable.

### Steps to reproduce

1. Create a sync for a directory with many files, using virtual files
2. Use "Always keep local" for a virtual file directory
3. Sync starts, crashes at one file (happens 100%), no error message

### Expected behavior

。。。

### Which files are affected by this bug

all

### Operating system

Windows

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

Windows10、Windows11

### Package

Official Windows MSI

### Nextcloud Server version

30.04

### Nextcloud Desktop Client version

3.15.0

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

Updated from a minor version (ex. 3.4.2 to 3.4.4)

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

Encryption is Disabled

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

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

### Nextcloud Server logs

```shell
none
```

### Additional info

[log.zip](https://github.com/user-attachments/files/18139129/log.zip)