Texture Problem
Are the button bases func_detail?
Yea but it happened on some other brushes that didnt have one of them next to it as well
I have a feeling that it might have to do something with the brush being warped somehow and it added in an extra face to the wall to compensate for it.
When you see this error, type in mat_wireframe 1. I cant duplicate this error whatsoever :S.
Picture Notes (brush on the left is affected, brush on the right is not, though its pretty obvious xD)
Actually you may be correct about func_detail, the other 2 brushes are next to the door frame which is func_detail. It was a little tricky to see with mat_wireframe 1 so this is mat_wireframe 2
It doesnt do it around all func_detail objects though and there are other door frames and button bases where it is fine. In a map im working on, one brush in the entire level is affected and its next to a func_detail that isnt even an unusual shape.
Also the reason I didnt fix those last 2 was because in Mevious' playthrough I noticed the indicator lights were gone even though they were fine in hammer, didnt realise func_brushes cant have overlays. Im not too worried, doesnt stand out too much in the destroyed style and as josepezdj says you could go crazy trying to fix every last detail in hammer 
Oh, so it's the T-junction fixer that's doing it.
That is a part of the compiling process that splits faces to remove T-junctions, which cause seams to appear between faces. Maybe one of those door vertices is just very slightly off-grid and skews the triangle next to it.
My 'weird wall' is next to a door frame too. Coincidentally, it's the only door frame in the whole map that I rotated after collapsing its instance. Lets try if the problem goes away if I reinsert the instance at the correct angle and re-collapse it...
Edit: Aaaaand we have our prime suspect. In my case, it turned out to be this ball button instance. (Notice the non-integer dimensions.)
Let's have a closer look at the corner:
If this touches a flat surface, it will warp it due to the aforementioned T-junction fixing.
So wherever you get this problem, follow the wireframe lines to any standard instance nearby (or anything collapsed or otherwise derived from one) and you will likely find the culprit.
Other Portal 2 maps: Medusa Glare
Portal 1 maps: Try Anything Twice | Manic Mechanic
Awesome find! Thanks Chicken and HMW for your perseverance! 
And ofc LoneWolf to go deeper into this 
Everything well noted!
useful tools and stuff here on TWP 
[spoiler]
[/spoiler]Thanks HMW just checked and that was exactly the case on every affected brush, the tiniest vertex nudge on grid size one and it was fine without the need to func_brush, I have since edited the cube button shell, at least I can blame valves shoddy brushwork rather than my own
Damn them. Making our walls slit diagonally n stuff.
Then again, this error now makes complete sense when you tie the wall to an entity instead of leaving it in world geometry. Func_details are just world brushes that vvis ignores.
So I hope this serves as a lesson. Always align to the grid - or prepare for unforseen consequences.
Wouold "smoothing groups" help with this weird cuttings and bad lighting/shadowing on brushes' surfaces? I remember I discovered this feature a while back when I was making The Second Exodus and I used it for every slanted brush I made (which was func_detailed btw)... and I don't remember to see this kind of weird stuff in the whole map...
I use to make my own button supports or door frames (and all the rest of brush work) and I am specially careful with all vertices, merging and snapping to the grid everything... so I can't understand why sometimes this simply appears...
useful tools and stuff here on TWP [spoiler]
[/spoiler]Damn them. Making our walls slit diagonally n stuff.
Then again, this error now makes complete sense when you tie the wall to an entity instead of leaving it in world geometry. Func_details are just world brushes that vvis ignores.
So I hope this serves as a lesson. Always align to the grid - or prepare for unforseen consequences.
The worst bit is how small they are off grid, its about 1/100th of one single unit off that point, its not even noticeable until you zoom in so far that size 1 grid units are huge. Still enough for hammer to get freaked, and yes, "Always align to the grid" a valuable lesson... that valve needs to learn