I'm attempting to create cardboard displays that require hemmed edges to provide structural rigidity. For this function, it is desirable to have an extremely tight radius so the material is folded over on itself. 

When I create an initial sheet metal part (Base-Flange1) the hem function works correctly as shown in Figure A. 

However, after extending the material creating Base-Flange2 the hem function no longer produces the desired results (ref. Figure B). 

Any suggestions are appreciated.