Replication issues & warnings if a client hitches while the server seamless travels

If a client hitches while a server performs a seamless travel, the client will get multiple lines of logspam of these warnings:

Warning: UActorChannel::ProcessBunch: SerializeNewActor failed to find/spawn actor
GetObjectFromNetGUID: Attempt to reassign read-only guid

Some functionality is also broken, for example in ShooterGame the client doesn't see the match countdown timer and can't move the spectator camera around.

This seems similar to [Link Removed] and https://udn.unrealengine.com/questions/581912/actor-randomly-not-replicating-after-seamless-trav.html but Jon's fix from that answer didn't help this issue.

1. Start 2 instances of ShooterGame
2. Have one host a LAN match on either map with any number of bots
3. Have the other join
4. Wait for the round to end (speed this up by entering "set ShooterGameMode RemainingTime 1" in the console on the server once the round starts)
5. Right before the post-match countdown gets to 0 and the map reloads, hitch the client for the duration of the server's load (it's seamless traveling). An easy way to do this on Windows is to click and hold on the title bar of the client game window - this will pause the game thread.
6. Once the server is loaded into the new match, resume the client