I have a weird issue. After I setted up my Owncloud account, I received address http://192.168.0.107 however after reboot it changed to http://192.168.0.103 and I can not login even with default password. (btw I already used and uploaded some files to 192.168.0.107)
But in my own point of view, you have configured the Univention Networking using DHCP, and if the IP is changing always in every restart, verify your DHCP Server and verify the configurations and/or add a fixed address rule for your univention machine.