This is basically CONTROLLER-1672 but that evolved into issues with datastore and jolokia reads; this is just a missing RPC response.
CONTROLLER-1665 is basically the same, it that was seen in different scenarios and is perhaps fixed by now, so not sure if this is a duplicate.

This happened on Sandbox, when the original module-based leader member-1 was isolated for a brief time. The unresponsive member was member-2, which stayed a Follower, but it is not clear whether it was considering member-3 as a Leader.
Karaf.log [0] is huge, the test started at 17:52:27,543

Writers on the other two members have reported [1] success.

[0] https://logs.opendaylight.org/sandbox/jenkins091/controller-csit-3node-clustering-only-carbon/6/odl2_karaf.log.gz
[1] https://logs.opendaylight.org/sandbox/jenkins091/controller-csit-3node-clustering-only-carbon/6/log.html.gz#s1-s10-t1-k2-k25-k1-k1