theres a file called where config.json you need to set custom stages to 0, it worked for me.

Note: to be honest i didn't know where to find it nor where to even start, so i did custom search of whole "Madness Project Nexus 2" folder through folder manager, and to my suprise it appears there was 2 identical files called config one was literally in Madness Project Nexus 2 folder (i thought it could be just an error and tried to run the game without it but NEM wouldn't work) and the other one in:

Madness Project Nexus/Madness Project Nexus_Data/Custom Stuff

and only when i set custom stages to 0 in both of the files, only then it worked. no idea if its useful or maybe you just knew that already, but just keep in mind it may be the case for you too...?

even though this could turn off the custom stages, for some reason i have a bug where my camera just gets stuck in the floor (apparently in the 3 arena stages as far as i noticed)
but i hope i could help.

引用自 EvoNI'：

even though this could turn off the custom stages, for some reason i have a bug where my camera just gets stuck in the floor (apparently in the 3 arena stages as far as i noticed)
but i hope i could help.

The rooms folder may be missing from the custom stuff directory.

well all i did is replace the folders when NEM updated like usual, cant tell for sure but they're there as far as i know, atleast i definitely didn't mod/delete or even touch them.

IF they ARE missing somehow, what do i do then?

just checked rooms folder seems to be there no idea why it doesnt work

im assuming they are just broken, but they are for there for sure. i didnt try deleting them yet, maybe that would solve the issue. still though, you gotta answer people more dude