I have feature services published to an internal portal that over time lose feature layers for some reason, and thus break the web maps using those feature services. What causes a feature layer, that has no changes to it at all get dropped or lost from a feature service? There were no changes made to the feature service, or the web map consuming the feature service, and the web map worked for several months, then all of a sudden stopped working, and in investigating I found that one of the feature services had missing feature layers that had been there and working before. No database changes were made to the schema, only data uploads were performed. I see this after the feature service has been published and sitting in the portal for a few weeks to a few months.