When a PushTarget renders, it fires up a cometd connection to receive updates. At this point it registers the page activation context.
serverside push events fire a component event. But before this, tapestry first fires the onActivate with the push target's page activation context. >From your earlier comments, the form submission is not ajax. So I can only assume a new page render occurs after onSuccess (with a new PushTarget). There's likely a situation where the serverside is attempting to push to the old PushTarget (with the old page activation context value) before the page refreshes.
