From what you write in your other question over here, I’d also conclude you’re using WebDAV to provide the virtual drive.
Note the difference: You’re not using WebDAV to sync your data, but you’ve chosen WebDAV within Cryptomator’s settings as the drive type.
If you’ve installed Dokany (comes bundled with the installer), you can use Dokany instead of WebDAV, which doesn’t have the aforementioned issues with the C:\ drive capacitiy.