idk if it's the glitch or not, but during doom 2 stage 4, some switch doesn't work properly. (One switch should put the box down, but it rarely does it.)

Does it simply reboots? I had this happen with Duke Nukem

The master levels are Doom 2 PWADs (patch-WADs) and not IWADs. They're not complete WAD files and cannot be run alone.

They are designed to be loaded over an allready loaded Doom 2 IWAD.

So when starting nDoom, just select the original doom2.wad.
On the next screen, press tab to load a PWAD and choose one or several of the Doom 2 master levels PWAD.

Then choose the starting map and skill level and you can launch your patched Doom 2 game.

Would there be a way to make this run with nDoom ?
I downloaded it, but there is no "wad" file inside
It runs with gzdoom and needs a doom2 iwad.