Can't export a file to a cloud (mounted via WebDAV - RaiDrive)

Okay, so. I have sucessfully mounted my Nextcloud to Windows via Raidrive (WebDAV). There is a folder that was shared to me, I have all the neccessary permissions for this folder. I can copy files into this folder, I can modify the files there, I can delete the files, I can copy the files from there to my PC.

The only problem I have is that for whatever reason, I can’t export files from different apps directly into the shared folder on this cloud. It says I don’t have permissions to modify the files in there and that I should ask the server administrator.

What I have to do is export the file to my desktop instead (or anywhere) and then move them into the shared folder on the cloud (still via WebDAV).

I really need a fix for this. It is crucial for me to export files directly into the shared folder. Any ideas?

Screenshot with the error message is in czech, however it says what I wrote above. (you don’t have permissions to modify the files, ask the administrator etc.)