I also have this problem trying to make a computer screen. Whenever I try to make a rectangle with a caved-in portion in the middle (like a simple rectangle picture frame) two corners try to be difficult and won’t cave in. Instead of a 90 degree angled corner like I want, it’ll give me a corner that looks like someone took a triangle and stuck it in there. What am I doing wrong?
Hard to say. A picture will be worth a thousand words, a copy of the .blend worth 100,000
Okay, here’s a picture:
See the two messed up corners? I can’t see why they aren’t like the others. A simple computer screen is doing the same thing.
I’d say you have a rogue face in there; its folding over and creating the triangle instead of extruding smoothly. How to fix, depends on what you did, for that You’ll need to share the .blend file