Call Manager 4.2 database issue after a publisher failure

This is a post for future reference. A customer of mine experienced some strange symptoms on their CUCM’s this week. And it took me some time to figure out what and why.
Issue at hand: When logging on to ccmadmin on the publisher, several ip-phones where not registered. But the phones were operational, and showed no sign of error. When logging on to the subscriber, I found all of the “not registered” phones registered. But all phones registered on the publisher was here “not registered”.
Troubleshooting: I tried booting the CUCMs but it did not help. I tried to restart services and manually fail over phones to one of the CUCMs. But the result was always the same. Whichever CUCM which did not have the phones registered, listed the phones as "not registered”.
Resolution: I’ve seen this before, and suspected a broken SQL link. Running DBHelper confirmed my suspicions, and fixed part of my problems. After recreating the publish/subscribe link in SQL, I expected the call managers to perform normally. But not so. I then booted the subscriber, but nothing changed. Only after booting the publisher first, then followed by the subscriber fixed the problem entirely.