how keep unbound up if internet down ?

[sean darcy]

Fedora 29, unbound 1.8.3

A machine rebooted while we had a brief (20 second ) glitch in our router.

systemd[1]: Starting Unbound recursive Domain Name Server...
Apr 23 18:49:54 asterisk unbound-checkconf[957]: unbound-checkconf: no 
errors in /etc/unbound/unbound.conf
Apr 23 18:50:10 asterisk systemd[1]: Started Unbound recursive Domain 
Name Server.
Apr 23 18:50:10 asterisk unbound[1282]: [1282:0] notice: init module 0: 
ipsecmod
Apr 23 18:50:10 asterisk unbound[1282]: [1282:0] notice: init module 1: 
validator
Apr 23 18:50:10 asterisk unbound[1282]: [1282:0] notice: init module 2: 
iterator
Apr 23 18:50:10 asterisk unbound[1282]: [1282:0] info: start of service 
(unbound 1.8.3).
Apr 23 18:50:10 asterisk unbound[1282]: [1282:0] info: generate keytag 
query _ta-4f66. NULL IN
Apr 23 18:50:33 asterisk unbound[1282]: [1282:0] error: .: failed 
lookup, cannot probe to master c.root-servers.net
Apr 23 18:50:33 asterisk unbound[1282]: [1282:0] error: .: failed 
lookup, cannot probe to master b.root-servers.net
Apr 23 18:50:36 asterisk unbound[1282]: [1282:0] notice: sendto failed: 
Address family not supported by protocol
Apr 23 18:50:36 asterisk unbound[1282]: [1282:0] notice: remote address 
is (inet_ntop error) port 48988
Apr 23 18:50:36 asterisk systemd[1]: unbound.service: Main process 
exited, code=killed, status=11/SEGV
Apr 23 18:50:36 asterisk systemd[1]: unbound.service: Failed with result 
'signal'.

The router came up about 5 seconds later.

How do I /can I configure unbound so that it keeps trying for at least 
some period of time ? This is actually a remote machine, but by sheer 
luck one of our guys was there. The only thing the users knew was that 
nothing worked, even though the net was up.

Any help appreciated.