Field Maps Designer - List contains errors

[LanaJewell]

Hello all, 

I was converting pop-ups to forms in field maps designer for several layers which are all part of the same hosted feature service. All succeeded except one, which refused to save. After some poking around, one of the fields in this form (which has a couple thousand options in a domain) showed this error which is apparently enough to block the entire form from being created:

Is there any way to view the error, either in field maps designer or out of it? It's never caused a problem being used as a pop-up, but I'm looking to add form functionality to a different aspect of this layer and can't find my way around this. 

[LanaJewell · Accepted solution]

To anyone running into the same thing--I found my answer and my workaround.

This layer was referenced in ArcGIS Online as a distributed collaboration from our ArcGIS Enterprise. Since technically the Portal/Enterprise side of things is the one who "owned" the layer, the list is not visible/editable in AGOL. However, I was able to access the domain/data that the Enterprise layer was created from. I made a copy of the schema used to create this layer, hosted my own layer in AGOL with no Enterprise connection, and then attempted to make changes. Now the list was both viewable and editable--there were a few dozen rows that had unique domain codes but not domain values, which was causing the error. I was able to then revise the list for the next time the Portal data was rehosted. 

My suggestion to Esri: Can we please at least have the list errors be viewable, even if the list is not editable? That would've saved some troubleshooting in my rehost workaround.