This sounds more like misconfiguration to me. Can you provide doveconf -n and full output of namei -vl /full/path/to/mailbox
-------- Original message --------
From: Yves Goergen <nospam.list@unclassified.de> 
Date: 19/05/2018  18:51  (GMT+02:00) 
To: Dovecot Mailing List <dovecot@dovecot.org> 
Subject: Re: Cannot delete folder