Seamless travel seems to not be functioning properly. With Run Under One Process set to false and Seamless travel enabled, the ServerTravel command is not bringing the server to the specified map. With seamless travel set to false the host is able to connect to the new map but the client remains on the initial map. The issue occurred with or without a transition map specified.
The log shows this warning even when Run Under One Process is set to false:
This issue is occurring in //UE4/Release-4.26 @ CL 16018004
This issue is occurring in //UE4/Release-4.25 @ CL 14818863
Not a Regression
Seamless travel does not occur and the server remains on the first map
Seamless travel occurs and the client and host are brought to Map01
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-115324 in the post.