I added a couple of editable feature layers to my map to be fed into my sidebar instant app. The first feature you click on seems fine -- the attributes pop up in the side bar, you can edit them and save them and that seems fine. But when you select another feature to edit, you just get a spinning icon. This happens whether or not you edit the first feature, but even if you just click from one feature to the next. It happens in other apps as well with different feature layers, so it doesn't seem to be a glitch exclusive to the data or app. Once you refresh the page, you can select and edit a new feature.
