I would have watch -d -n1 "netstat -na| grep :257" on both a gateway and the SmartCenter.
Then fetch policy on the gateway.
If nothing stands out then you should stop and start the gateway and see if anything stands out.
While sk100538 may be helpfull it will not resolve all issues. I have seen a weird case where the TAC was scratching their heads as much as I was.
A recent HFA fixed it.But the issue was no on the list for R77.30.
So to be honest I still don't know why it was solved but it never reappeared either.
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