I am cloning content from AGOL to a new Portal (10.8.1) in Azure. When attempting to clone a feature layer, it fails with
ERROR: Inconsistency in the Field Definitions found. Failed to execute (Manage Feature Service)
I am using clone_items as described in Cloning Content | ArcGIS for Developers. The same code works in the other direction if I clone a feature layer from Portal to AGOL.
I also tried ArcGIS Online Assistant (esri.com) but had the same results for both directions. I notice that it provides two options (Item Copy and Full Copy) only when going from Portal to AGOL. Full Copy worked for Portal to AGOL.
This posting sounds similar: Can't move a Feature Service using ago - Esri Community