Just importing a large CSV (ONSPD https://ons.maps.arcgis.com/home/item.html?id=8da1cb5b6daa4d72b8bbef115cf26746 ) and started by renaming the fields but update of the field list stopped. Saved reloaded, same problem as new renames were not kept. Added a clean step then the above vague error was shown in the Notifications, no detail and nothing to see.
I've exported the flow with the data and attached but all seems hidden. Anyone else seen this?
I have not seen or found any other reports of this specific error.
Please open a support case if you have not already. The team would love to coordinate with you on this unexpected behavior to help gather some information and provide some explanation of what is occurring.