I'm sure this is a tired question on here, but having scrubbed through a few on here I haven't find an answer directly for this issue.
In baking a normal map, the content bakes perfectly fine but it's perspective is skewed.
As you can see, the second picture appears to have baked an orthographic perspective that is NOT perpendicular to the normal of the face, it's as if it's coming from the top left of the frame. I'm wondering HOW this came about, as the Normals are perpendicular, the UV isn't skewed and the bake is just done as any other object. What caused this?
Courtesy of Lemon!
This resolved the issue. I applied an edge split as per the post, but am still unable to really understand WHY that worked. There were no hidden or squashed faces, the face in question is planar (scale y 0 and apply scale changed nothing) and yet it still baked as if it weren't. Odd for sure, but at least there's the solution.