So I'm stuck with a problem I can't solve. I'm trying to cut a 45 degree (basically a miter) into this face with the linear holes punched down it. The end goal is to have the face with the holes at 90 degrees from the static side that doesn't get bent. My game plan was to miter the bend on the far left of the drawing below

So far so good. From here I unfolded the part and created a cut extrude

Refold it....

And not its off the right angle it was before...

I can't wrap my head around whats happening here. Any help would be much appreciated!