Asynchronous Level Travel

Development Programming & Scripting
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1

My setup is as follows:
I press a button on my widget to try a hero:

void UHeroInfoWidget::OnTryHeroButtonPressed()
{
	UTBCGameInstance* GameInstance{GetGameInstance<UTBCGameInstance>()};
	_LIKELY if (GameInstance)
	{
		GameInstance->SetPlayerCharacterClass(HeroInfo.CharacterClass.Get());

		GameInstance->AsyncLoadMap(TryHeroLevel);
	}
}

It asynchronously loads TSoftObjectPtr TryHeroLevel map:

void UTBCGameInstance::AsyncLoadMap(const TSoftObjectPtr<UWorld>& Map, const bool bShowMapAfterLoad)
{
	const FLoadPackageAsyncDelegate LoadDelegate{
		FLoadPackageAsyncDelegate::CreateUObject(
			this, &UTBCGameInstance::OnAsyncLoadMapCompleted, bShowMapAfterLoad)
	};

	LoadPackageAsync(Map.GetLongPackageName(), LoadDelegate, PKG_ContainsMap);
}

void UTBCGameInstance::OnAsyncLoadMapCompleted(const FName& PackageName, UPackage* LoadedPackage,
                                               const EAsyncLoadingResult::Type Result,
                                               const bool bShowMapAfterLoad) const
{
	if (Result == EAsyncLoadingResult::Succeeded && bShowMapAfterLoad)
	{
		UGameplayStatics::OpenLevel(this, PackageName);
	}
}

It works as intended, main game thread doesn’t lock, nothing freezes.
However, I face a problem when trying to enter a TransitionLevel while TryHeroLevel is loading.
If I add a OpenLevel synchronous function in widget like so:

void UHeroInfoWidget::OnTryHeroButtonPressed()
{
	UTBCGameInstance* GameInstance{GetGameInstance<UTBCGameInstance>()};
	_LIKELY if (GameInstance)
	{
		GameInstance->SetPlayerCharacterClass(HeroInfo.CharacterClass.Get());

		UGameplayStatics::OpenLevelBySoftObjectPtr(GetWorld(), GameInstance->GetTransitionMap());

		GameInstance->AsyncLoadMap(TryHeroLevel);
	}
}

my main thread freezes, I see transition map for a slight moment before being moved to TryHero level. I’m not sure how to handle this correctly besides just adding TransitionWidget on screen and not moving to TransitionLevel. Any insights?