Weird Translocations on Play

[IanTanthal]

Greetings, fellow survivors and modders!

I recently began to create my very own map, just because i already was interested in stuff like this a loooooong time ago.
After fiddling around and moving the DevKit to my SSD (because crashes and long waiting times), i began with the terrain etc.
So far so good, it looks pretty solid in my opinion.
BUT
As i was nearly finished with the second layer of foliage (the near ones), i decided to take a look ingame.
What happened just threw me away like a stone.
 

The entire foliage was moved from this point.
The terrain travels to a completely different location in Play Mode.
Toggling the levels also doesn't work anymore. They disappear, but to get them back again, i have to restart the whole editor.
Did i do something wrong?
(Foliage is split into levels - just as on TheIsland)

 

Thanks in advance!

EDIT: Seems like the image attachment is broken. So here are links:
http://baneofthelegion.de/uploads/UE4Editor_2017-04-14_12-02-20.png (On Play)
http://baneofthelegion.de/uploads/UE4Editor_2017-04-14_12-02-33.jpg (In Editor)