The metadata on features is removed if the features are added through My Content in ArcGIS Online as a zipped file geodatabase.
Last Published: November 11, 2014ArcGIS Online
Bug ID Number
October 13, 2014
February 13, 2023
After review by the development team, it has been determined that this issue is related to a known limitation with the software that lies outside of Esri's control. The issue's Additional Information section may contain further explanation.