https://support.esri.com/en-us/bug/when-adding-an-item-to-content-in-arcgis-online-with-a-bug-000107749
BUG-000107749 for ArcGIS Online
When adding an item to Content in ArcGIS Online with a file name that is completely contained within the name of an existing file, the following error message...
bugarcgisonline