ZDoom

[quote="_mental_"]As for other glitch, I have no idea.[/quote]
It's weird indeed, and it's not just me. I just finished watching a stream of my mod and the same thing happened on MAP25 Cat and Mouse on the hidden walls, so it's got to be related to this midtexture thing in some way, [s]maybe an AMD bug? I don't know what GPU they have.[/s] yea it's got to be an AMD bug. The other guy has an HD 7970 and it happens with that card too.

In general, it should be said that using mid textures that extend beyond the real ceiling into the sky part is entirely undefined. We've had several issues with that over the years but the original implementation was far too sloppy to make it robust.

Fixed it in my map by adding an unseen upper texture to both sides of the linedefs. This also fixed the graphical glitch.

The bug was in textures didn't go into the sky.

Not sure that I'm following. Is the bug that they didn't go into the sky forever or that they did? Because in this map they should not be that tall, so if that was the bug then it's not fixed in my case. I guess that means I need to define a copy of this grate that is taller and then don't wrap it?

It was [url=https://forum.zdoom.org/viewtopic.php?t=58311]this bug[/url]. Software renderer had explicit handling for walls with wrapped mid and without upper textures. I did the same for OpenGL one.
And since GZDoom 3.2.5 the blue key grate in the given map is identical with both renderers.

As for other glitch, I have no idea. This is how it looks for me with 3.2.5 x64[attachment=0]Screenshot_Doom_20180207_095546.jpg[/attachment]

Just noticed this really weird effect on this midtexture that meets with sky. In older GZDoom versions (2.2.0 confirmed) the midtexture stops at the point where sky meets the wall as expected, but on 3.2.5 it seems to continue into the sky infinitely (or to maximum map Z height). Also some graphical glitching on the midtexture that might not be related (also does not occur on 2.2.0). These screenshots explain it all.

[url]https://imgur.com/a/jAiSa[/url]

This is on map "OUT07" of my Doom 64 TC, which you can find here:
[url]http://www.moddb.com/mods/doom-64-retribution/downloads/doom-64-retribution-version-14a[/url]