It's an old question for which you might have found a solution... If not:

Are you using a cluster or single server

you could try with DSS

prconfig/server-push/enabled/default set to false (or set it to true if you need this push engine)

If I remember well, I've set to false above settings after same kind of issue.

I think that push engine is for notification, operator presence and other things (I don't know well)

Since we don't use this, I disabled it Well, you could try, it's an easy check

regards

Anthony