I can't fix this texture bug

[ChestedArmor]

In the preview of Ultimate Doom Builder the iron grid textures load properly,

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but when I start the game, it loads for some reason these textures

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One time it magically fixed itself, but after importanting some files into the wad it came back.

 

I honestly don't know what causes it, it could be pretty much anything, because I imported 3 custom enemies, a truckload of custom textures and some levelspecific scripts into the wad and the magic fix happened when I deleted some unused textures(!?)

 

It only shows this error message, maybe it has to do something with that: 

Patch "SW18_7", index 2314 is double defined in resource "DOOM2.WAD"

[Gothic]

There may be 2 patches with the same name in your file. Check for duplicate names with Slade3:

[ChestedArmor]

I just added the texture of the gate again and now it works lol.  

[ChestedArmor]

@Gothic Slade seems to have a loose interpretation of "unused textures", because my level is an error plantage now