Hello, I had the problem, that the Homematic-Bridge was gone away after a reboot of the pri. I read, I have to remove the /sevices/addons.cfg, which did. I testet by rebooting and installing the bridge via PaperUI. Reboot, Bridge still there, everything OK.
Some days late I rebooted again, and the Bridge was gone.
The Items (Window Contacts) are defined inside the Items part off the designer.
What am I doing wrong? There must be a way to “keep” the Bridge after the installation??
I have the same issue, and it seems that the Homematic Bridge changes ID. One can still see the old bridge with ID but not active. After checking the inbox manually a new Homematic bridge appreas with new ID. Once activates all sensors apprear as new things and need to be configures again 
is there any way to fix this ?