Homeassistant:8123 url stopped working

this is a recurring problem for me after an upgrade. While I am able to access my homeassistant instance via my xxxx.duckdns.org URL it does not respond to the homeassistant.local:8123 or the IP address (I have assigned a static one). Usually it works after a couple or more of reboots but this time no…I went from version 0.11.4 to 0.12.2. there have been no changes to the router.
While it may eventually work is there an explanation to this? Is it something in my configuration that causes this? I would appreciate any help I can receive on this.

many thanks, yannis