[nsd-users] "update failed (acquired: 1406646354), restarting transfer (notified zone)"

[Stephane Bortzmeyer]

A NSD 3.2.16, secondary for a large zone, suddenly stopped updating
the zone:

xfrd: zone foobar.example: soa serial 2222549638 update failed (acquired: 1406646354), restarting transfer (notified zone)

Other (smaller) zones on the same machine are properly updated.

Checking the source code (xfrd.c) does not give me many
hints. "acquired" is the time where the SOA was acquired but it it not
clear what is wrong exactly, and how to solve it. Did anyone see such
behavior?