imSCP 1.5.3
Debian 9
not sure if it's a bug or not ...
after upgrading 1.5.3 to latest 1.5.3 (build 2018120800) everything went fine when I then wanted to change dovecot and php-fcid:
perl imscp-autoinstall --debug --reconfigure
perl imscp-autoinstall -d worked after that, but it seems changing from courier to dovecot and/or php-fcgi to php-fpm produced this issue.