Accounting replication issue

[Chris Adams]

I have two servers running FreeRADIUS (CentOS 7 with freeradius-3.0.4).
They are logging accounting records to local MySQL servers.  For
redundancy, I configured FreeRADIUS to replicate the accounting records
to each other, based on the robust-proxy-accounting sample config.

This works, except when one server is unavailable (call it server A),
the other (server B) stops replicating the records until I restart
FreeRADIUS on server B.  Server B logs that server A went away, and logs
that it came back (in this case, somebody did something dumb on server A
and triggered the kernel oom_killer - didn't touch the FreeRADIUS or
MySQL processes, just the dumb grep):

Jul 24 09:25:38 srvB radiusd[20768]: Marking home server srvA port 1813 as zombie (it has not responded in 6.000000 seconds).
Jul 24 09:25:38 srvB radiusd[20768]: (52212975) ERROR: Failing proxied request, due to lack of any response from home server srvA port 1813
Jul 24 09:25:42 srvB radiusd[20768]: No response to status check 52213042 for home server srvA port 1813
Jul 24 09:26:05 srvB radiusd[20768]: No outstanding request was found for reply from host srvA port 1813 - ID 197
Jul 24 09:26:06 srvB radiusd[20768]: No outstanding request was found for reply from host srvA port 1813 - ID 198
Jul 24 09:26:06 srvB radiusd[20768]: (52213350) Received response to status check 52213350 (1 in current sequence)
Jul 24 09:26:06 srvB radiusd[20768]: (52213350) Marking home server srvA port 1813 alive

The comments in the sample config just say "When the home servers come
back up, the packets are forwarded, and the detail file processed as
normal." - I don't see any configuration related to that, but it
defintely did not happen for me; the records were just written to the
detail file until I restarted the service (which then processed the
backlog correctly).

Any suggestions for what to look at?
-- 
Chris Adams <linux at cmadams.net>