@Peter Koltl - it's certainly a non-standard arrangement not having two MnT nodes, but I am sure it's not the reason why the Services node stopped replicating.
Having one MnT is perfectly legal. Imagine the scenario where two have two MnT nodes and you pull the plug on one of them. Then you are left with one MnT. it doesn't mean the system will stop working. If it does, then I am really worried.
There is probably some log or support bundle that contains the reason for the replication failure. You'd hope the TAC would be able to tell you what happened but most users should be able to inspect the support bundle of the PAN node to see why it's not happy.
I am sure the TAC have a nice cheat sheet that tells them which log is used for which purpose. That would be an awesome cheat sheet to have. The log file names are not always self explanatory. And the logs files will often contain some pretty hairy data.
I have seen nodes stop replicating a few times. Never got to the bottom of the issue. I just hit manual sync and that sorted it. I would recommend getting hold of TAC
