Yes! That did it!

I displayed my level_ent.min_x and level_ent.max_x
and it was suspiciously close to the deadzone

I then placed some blocks in every corner, compiled it and now the values of
level_ent.min_x and level_ent.max_x
went up remarkebly.
And it works perfectly fine now.

All that was in my map previously was terrain, so I guess the values of level_ent.min_x and level_ent.max_x were smaller than my terrain?
Anyway:
I learned something new today and this is very useful to know !

Thank you guys, I will not forget this!