I solved it. For some reason, the AcquisitionObjectTypes was filled with WorldDynamic, which initially my new castle class did not use as object type. The object type previously was World static, because I chose the preset “Block all”, which uses World static.
However, I never touched the AcquisitionObjectTypes object and did not find any assignment to AcquisitionObjectTypes using Visual Studio. Neither do I find an assignment in the blueprint editor. I do not know why this array even had one entry. It was declared as
/\*\* Types of actors to filter for when trying to find targets in the acquisition radius. \*/ `UPROPERTY(BlueprintReadWrite, Category = "RTS")` TArray<TEnumAsByte<EObjectTypeQuery>> AcquisitionObjectTypes;
Really strange, maybe someday I find out where it gets its element from (it has exactly one).