Server Travel

I have become stuck with my project all thanks to Server Travel and i can not find much info on it online ill go through my setup and hopefully someone can tell me what i am doing wrong
1.I have a Lobby game mode that has use seamless travel ticked
2. i have an execute console command that reads (ServerTravel Arena01) in side the box map being arena 01
3. When i am in the lobby both players are connected its only when i fire off the server travel command with the launch the game button it crashes
if i change it to open level then only one of the connected comes the other returns to main menu
also if i use server travel i get a fetal error on both screen when trying to get to Arena 01