On a Detail page, IDs might be displayed instead of labels intermittently when using a nested relation to the associated Entity definition. The issue occurs if the Label property that is used in the Display template of the associated Entity definition has not been included in the nested relation configuration.
If configuring a nested relation without adding the property or properties used in the Display template of the associated Entity definition, there is no advantage of the relation being nested. In this case, calls that use the associated Entity definition might slow down, and additional requests to the server are needed to fetch the correct display properties.
To resolve the issue, add Label as a nested property:
Note: If you need to add any other property or properties that are used in the Display template of the associated Entity definition as nested, make sure that you follow steps 1-8 for those properties as well.