Cook Map Extension broken? Devkit problem?

Hey guys got a question.

Is it possible that the Map Extension cooking / all map extension mod are broken with the new Devkit?
I just update my mod (without any changes just for Devkit update) an now it will only work if i cook my mod als “Cook Gamemode”.
Before the update it works as a Map Extension without any problem.
Now i have to delete my costum supplydrops submap because i cant use it with any other mod.

Maybe someone of you got some tips/fixes for me?