ServerTravel from a map with a GameMode set to Use Seamless Travel and then ServerTravel back from a map without Seamless Travel enabled will crash the editor

ServerTravel from a map with a GameMode set to Use Seamless Travel and then ServerTravel back from a map without Seamless Travel enabled will crash the editor.

Reproduced in 4.7.1 binary and Main (//depot/UE4/Promotable-CL-2455917)

Unable to include Crash Report... Crash Reporter keeps crashing in Main for me. Crash log attached.

1. Create a new blank project
2. Save the map as NewMap
3. Create a new GameMode BP
4. In the BP defaults, enable Use Seamless Travel
5. In World Settings, set the GameMode to the new GameMode BP
6. Create a new level
7. Save the level as NewMap2
8. Open NewMap
9. PIE
10. Enter console command, "ServerTravel newmap2"
11. After NewMap2 is loaded, enter console command, "ServerTravel newmap"

Result:
Crash

4.8.0 p3: default pawns don't spawn on clients after seamless ServerTravel

Engine Crash when using Servertravel/Open on TransitionMap set in DefaultEngine.ini

[Crash] Using ServerTravel in Blueprint with a Client connected

Engine Crash when using Servertravel/Open on TransitionMap set in DefaultEngine.ini