Hello here!
At this point I am not sure what is going on 
Yesterday I was able to make it run, now this morning unbound is halted again.
What shall I look at for some debugging?
Hi,
Unbound logs to /var/log/messages, so running
grep -i unbound /var/log/messages
will return any messages logged by it. Please provide these here, so we can start investigating what is going in your case.
Generally, however, I am not aware of any general Unbound issues in Core Update 188. 
Thanks, and best regards,
Peter Müller
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