Same Problem,
it seems that the problem happen when you have 2 or more dns
The reverse dns try to write dato on the first (ina alphabeticcaly order) zone in DNS
in my case : alex.int, alex.net, everithing is working fine
but if the zones are :
aaa.at, alex.int, alex.net, reverse dns try to write data on aaa.at
My friends in zentyal are still working on it