I use an ASUS Router RT66 in connection with a synology station, where webdav is running.
All is configured and if I connect from outside, over the internet, all works fine.
I use https with port 5006. If i try to connect with my mobile inside the own network, it does not work. I will be asked for a password, but this will not be accept.
At home I use the the same configuration with the synology station. It works fine over internet and in the local network. The only difference is the router. Could it be a DNS issue?