On some cases, when decomposing corners, the shape changes to something different (G4). On other cases it works just fine. I couldn’t figure out what the pattern is for the cases where it doesn’t work, yet I figured when I change the alignment to X it works just fine.
For some reason “decompose corners” doesn’t work for me properly at all. Here is two examples of a “v”. The first one without any anchors in the _corner. glyph and second one with origin, left and right.