Show a note somewhere, if the number of coded domains exceed the settings for the map image layer. ->
Map Image Layer Pop Up's - Esri Community
Proposed Messages:
- in the Server Manager Logs ("Number of coded domains exceeds the specified limit. Adjust the value in the Service properties")
- in the Map Viewer ("Can not load coded domains. Contact your ArcGIS Administrator to increase the number of coded domains")
- somewhere in the service admin url or service properties url
