So to keep it short, i will just tell you how it happened.
I was building a wooden coaster in the custom editor.
i wanted to snap the track to the grid,
so i pressed the botton (snap to grid).
My selected track length was already short, so when snapped, it was snapped to zero(no length) .
then the camera and fuctions froze. the map began deloading. luckily i could stil escape the build menu, and it went back to normal
just to let you know. Hope it gets fixed!
kind regards :)