Reliable NetMulticast UFUNCTION only called twice

So basicly I have a function that sends all clients and the server an block update and or creation:

In the .H:

UFUNCTION(Reliable, NetMulticast) // Sends block update to clients
	void UpdateBlockToClients(const FString& Position, int32 ID);
void UpdateBlockToClients_Implementation(const FString& Position, int32 ID);

In the CPP:

void APlayerCharacter::UpdateBlockToClients_Implementation(const FString& Position, int32 ID)
	if (PP_BlockID.Contains(Position))
		PP_BlockID[Position] = ID;
		PP_BlockID.Add(Position, ID);
	GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, FString::Printf(TEXT("Position: %s, ID: %d"), *Position, ID));

Howerer when an block update is sent the debug message in the last line is only visible twice (including server) REGARDLESS of the actual amount of clients.

For example with 2 Clients and a dedicated server the funcion is called only on the dedicated server and 1 client.

Thanks in advance!