I am having problems with Page Test preview thumbnails using the Experience Editor. When I click Create -> Page Test, the thumbnail doesn't load and I can see using F12 in my browser that Sitecore keeps calling /sitecore/shell/api/ct/TestThumbnails/TryFinishGetThumbnails in an infinite loop. Am I missing any browser requirements here? I have tried with Sitecore 8 updates 2 and 3, Chrome, IE and Firefox. Anyone having this issue? It also happens when I try to approve an item with test in JetStream and it doesn't let me have an actual test started.