such an error in the program is unacceptable
Try editing the flat patten and unticking the corner treatment.
Its caught me out a few times in the past.
corner treatment was selected.
after editing the document properties > OK > save as > part template (file.prtdot) ...
Untick Simplify bends in the Flat pattern options.
does not help
apply "open bend region" in your closed corner options...relief is added when the Open bend region option is checked
The corner between bends is the one spot that can't be edited in the flat or in 3D. That spot must be handled by features in the software like close corners and how the flanges are added. Limit of parasolid sheet metal. Solid Edge has the exact same problems. Taking material away is never a problem, but adding material to that corner can't be done manually.
To help with the issue, you have to decide how to make the part. What is the sequence of events. Tab or contoured flange as the fist step. What is the sequence of flanges. etc.
Here is one strange work around for you (Sucks in drafting).
make a sketch of rectagle, say a 1' square. Add 0.01 radius to the rectangle. make a tab. Pull 8 flanges at once (4 radius, 4 sides). Undfold. cut, refold.
Note. the flanges have to be the way outside flavor. So I use the trick of offsetting the desired rectangle to the side a setback (Radius+ Thickness)
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