Change of listening port on Nextcloud - Copy and paste from IRC

[12:27] <chefboyct_> I have a quick question concerning Nextcloud Android app. I did set up my nextcloud to use listening port say 12345 via SSL connection. so when I connect to the application for instance. It works on the local network but when it is in mobile mode. it works randomly or it doesnt work at all. It will establish secure SSL connection but from time to time it will say connection timeout when it is
[12:27] <chefboyct_> connecting / authenticating. And if I can manage to log into the port 12345 … Android application doesnt really show preview of the files and when you download a file it also doesnt open automaically and I had to manually select option and choose an application (picture viewer on android ) for example. But itworks fine on the local network
[12:28] <chefboyct_> I have the same issues for a while as it has been very temperamental. But if I change back to standard port 80 and 443, then it works 100% and I dont (of course) have to specify port number to access (and please note that I have forwarded on the router as well as on the UFW) to test on 12345 port
[12:29] <chefboyct_> I would like to know if it might be bug related as I found on the internet somewhere also mentioned something as such. It is just so strange and unstable when you change the standard listening port to something else. and I am only using the Webserver on it as a cloud server

Using latest nextcloud 11.01 via apache2 and on Zorin (ubuntu)