I have this same issue on my install, but do not have Summerset Isle. It stutters and freezes for about 3 seconds before working correctly. My initial thought was that it may be a bad interaction with Extended UI (Only because I remember starting to see it when I started using Extended UI, but it was a while ago, so I am not sure.) and something else, but I have not tested that yet. Too busy trying to figure out why DYNDOLoad hard crashes my game after 10 minutes of play, indoor or out.