I am calling
GetWorld()->ServerTravel(travelURL,false,true); from within the GameMode,
but it disconnects all other Clients.
LogNet: Warning: Network Failure:
GameNetDriver[FailureReceived]: Host
closed the connection.
I already tried using Standalone game but that didn’t help.
I am using the Null OnlineSubSystem (LAN).
Any way to fix this?
maybe a stupid question but did u already figure it out? , because i have the same problem on 4.17.
Regards. Lex
Yes, I found the solution.
The signature of
UWorld::ServerTravel(String, bool, bool)
is somewhat confusing.
The last parameter is named bShouldSkipGameNotify, while the description of the parameter is
whether to notify the clients/game or not
As you can see, the name and the description is the opposite of each other.
You need to use false for the last parameter (if true, it won’t notify clients). Atleast that was my problem.
See my answer 
Oh my god, I wish I could upvote you a hundred times for this. Been fighting this same ■■■■, Googling furiously, and getting nowhere.