Can't delete former special folder, it keeps reappearing

[allgaeu_tobi]

I have created a folder "Spam" in the roundcube webmail and selected the newly created folder "Spam" under "Special Folders" for Junk.
Now under "Folders" the folder Spam is displayed with the icon for the Junk folder as desired and the old folder Junk is now a normal folder.
If I delete the Junk folder now, I get the confirmation "Folder successfully deleted" but immediately after deleting it is there again (visible after reloading the page).

[JohnDoh]

It will not be Roundcube that is doing that. It could be a plugin so try with disabled plugins. Do you have any other IMAP clients connected at the same time, may be its one of those. Or it could be the IMAP server itself. To confirm you can enable imap_debug in Roundcube. In that log you should see the folder delete command and the confirmation and also no folder create command.