Seamless traveling when joining sessions

I need to Seamless Travel using online sessions.

While ClientTravel is working when passing parameters TravelType and bSeamless, the JoinSession has no same parameters.

I tried to hack that by overriding ClientTravelInternal_Implementation:

void AVRPlayerController::ClientTravelInternal_Implementation(const FString& URL, ETravelType TravelType, bool bSeamless, FGuid MapPackageGuid)
	Super::ClientTravelInternal_Implementation(URL, ETravelType::TRAVEL_Relative, true, MapPackageGuid);

But after travel I returned to main map, not to server…
The online subsystem used is Null, but I will use Steam and other…

How can I fix this problem?