Why does STEP2 look weird here?

So, I've been working on a custom map which takes place in a spacestation via Doom Builder 2 and I created a border for a light that a Chaingun sits on and a platform for the spawn Teleporter to stand on. I applied STEP2 to the top and bottom of the sidedefs.

Now though, when I play it, the borders look really ugly, as though they're using STARBR2!


Here's what it looks like in Doom Builder 2:




Here's what it looks like in GLBoom:






Just what the heck is going on? Is it like that weird alignment glitch with FIREWAL*? (Which, I should remind you, only happens in Vanilla) Can I fix it with Slade?

Thanks in advance.

This thread should answer all your questions: http://www.doomworld.com/vb/doom-editing/61534-sudden-starbr2-appearance/

Are you using any custom textures or other resources in your map? Looks like some kind of texture conflict.

Might also be because of offsets, somehow. For whatever reason, the STEP2 texture has that STARBR2 patch (SW11_4) in its patch list, but it's behind the step patch (STEP03). If you've only got a map and no custom resources, it shouldn't appear, but who knows.

edit: Ah, Memfis has the answer, nevermind me!

edit2: That's a really interesting bug, explains why BIGDOOR7 displays properly in Doom 1 despite having a bad offset, and why some of the TEKWALL textures have a section where it looks like the texture has been doubled up.

In Slade, you can export STEP2 or any other affected textures as a single patch (right-click the texture's name in the TEXTURE1 editor, and Export or Extract), then just use that patch in place of the original composited texture so that it'll appear correctly regardless of which port you're playing in.

I vaguely remember having done this for STEP2 in cc4-tex.wad, but I might be wrong.