Getting SpawnObject wrong class: None error, but only in build

I am using a C++ class (inheriting directly from UObject) for a call to ConstructObject in BP. It constructs fine and operates correctly when run in-editor. However, when the game is built (Shipping), it does not work correctly, and I find the following error in the log:

LogScript:Error: UGameplayStatics::SpawnObject wrong class: None

I get no such entry in the editor’s log.

Potentially related information:

  1. ConstructObject is being called in a WidgetBlueprint. Does that not work correctly?
  2. I’ve already tried using an empty child BP class in place of the C++ class.
  3. I get no errors or warnings from the build log relating to that specific class.