Per https://udn.unrealengine.com/questions/329206/crashes-when-streaming-levels-in-414.html LevelCollections has introduced some issues with using Prepare/CommitMapChange.
CL# 3255445 has addressed the GetWorld() crashing issue, however, the ticking issue still needs to be addressed.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-40524 in the post.