I currently have published (non-hosted) feature service that connects to my enterprise geodatabase that is used to manage tree inventory data published using ArcGIS Server 10.9.1 and the feature service being added to ArcGIS Online. This feature service has three layers: 1 point feature class, 1 non-spatial related table, and 1 attachments table. The related table is a 1 to many relationship where 1 point (tree) can have many records (tree maintenance records).
I have instituted an attribute rule where the latest (or last added) maintenance record's "condition" field is used to attribute a "condition" field in the parent point feature class. This attribute rule works fine in ArcGIS Pro and the results from the attribute rule can be seen nearly automatically. The issue I am running into is when trying to test the workflow in ArcGIS Field Maps of adding a point --> adding maintenance record (or just adding a maintenance record to an existing point) and the maintenance record's attributes not being saved / sent / submitted on the first try. Only after the second attempt is the maintenance record's attributes being saved / sent / submitted and thus the attribute rule being executed.
It's unclear to me if its an attribute rule issue, a feature service issue, a data issue, or just a general bug / issue with my version of Field Maps.