You could try checking with gdb what the values are that are passed in the failing assert, maybe it provides clues.
-------- Original message --------
From: "Andre Hoepner - i.based: Systemhaus GmbH + Co. KG" <a.hoepner@ibased.de>
Date: 18/09/2018 19:57 (GMT+02:00)
To: dovecot@dovecot.org
Subject: Re: dovecot (2.2.13) panic on imap-login from iphone se
here is our config: (doveconf -n)