Funny enough i’m also stumbled on this while doing async wrapper for oss\findsessions.
But in my case i just forget to return array as const ref.
So, as it was, incorrect:
DECLARE_DYNAMIC_MULTICAST_DELEGATE_ThreeParams(FAsyncAction_CommonSession_FindSessionsCompleted, bool, bSucceeded, FText, ErrorMessage, TArray<UCommonSession_SearchResult*>, Results);
Correct way:
DECLARE_DYNAMIC_MULTICAST_DELEGATE_ThreeParams(FAsyncAction_CommonSession_FindSessionsCompleted, bool, bSucceeded, FText, ErrorMessage, const TArray<UCommonSession_SearchResult*>&, Results);
note: UCommonSession_SearchResult is an UCLASS(BlueprintType)