After password reset redirected to wrong URL



I have an issue: when users reset their passwords and click on “Reset password” button they are redirected to URL like this: 'https://FQDN:8080/owncloud/FQDN/owncloud/core/templates/403.php ( but password successfully reset)
The same situation i have with new user when he is trying to set password he is redirected to wrong URL.

Also if I use URL like this: 'https://FQDN/owncloud (without a slash at the end) I will be forwarded to the same URL ->https://FQDN:8080/owncloud/FQDN/owncloud/core/templates/403.php

If I use URL like this: 'https://FQDN/owncloud/ or 'https://FQDN/owncloud/login - everything is working and I see the main page of Owncloud.

Working URL:

I have:
owncloud version: (on docker container)
Univention App 4.3 Appliance owncloud (ESX)
start site has been changed to -> apache2/startsite=owncloud/login
Server is domain joined.

Owncloud app settings are:
owncloud_domain: 'https://FQDN (where fqdn is my external domain name)

All other settings are default.

Could you please tell me how to change URL on “reset password” ir “Set password” button, and how to force “https://FQDN/owncloud” URL forward to “https://FQDN/owncloud/login