It doesn’t look like Mordhau has official mod support (in that they’ve worked with Epic to provide an SDK for Mordhau using UE4)
You’re going to have to look at the Mordhau community guides/tools and see what they say about how to make stuff for it. From the log it looks like some of the code is different in the game vs. in the UE4 editor and it’s causing problems running your map.