Latest Tech Preview release appears to be causing problems with Plex Web.
1) Status log is filling up with "Unable to listen for events on "
2) Settings>Server>Check for update function never returns a response.
I think the latest WebKit builds are breaking things, the 1Password extension from AgileBits is also failing and this was acknowledged by the WebKit team.
Just a heads up if you are using the Safari Tech Previews and something doesn't look right. Quit and run the release version of Safari and the problem may go away...