I was traveling from the nether to the Overworld and back very quickly to make sure my portals were linked correctly. I did this multiple times, but after, like half an hour of this the game crashed and put me back a few minutes. 

Steps to Reproduce 

1. I was in creative mode
2. Travel very fast and within seconds of each time you go through the portal

this has happened to me twice, on copies of the same world
you have to travel a lot for it to happen
I think that’s it. Hope that’s enough info.