I have a published service layer working in a Collector map that coworker are using the field. Three of the four devices (iPhone 6s) are collecting data and syncing just fine in offline maps. There is one phone that just won't sync the data. We don't get any error messages, it just gets one-third of the way through the sync and freezes. Won't go any further. Does anyone have any suggestions on what to do or why this is happening?