I created a map service for Portal 10.8.1 (using ArcGIS Pro 2.6.3 from which I published). This map service contains 5 frequently used map layers, and they all draw to the screen exactly as expected after publishing. However, the next day two of these map layers always refuse to appear, whereas the other 3 are usually fine. If I republish the map service these reluctant layers do reappear, but the next day it's back to the 2 missing layers, which is most frustrating.
The only difference between these 2 map layers and the other 3 is that the popups have been customized (as opposed to using the default database tables/attributes), because there is no relevant data in these areas (just a name of what they represent).
Has anyone ever encountered this issue before? I have tried clearing the browser's cache, but this did not fix the problem. Surely I don't have to publish this one map service every day, correct?
Suggestions?