I have an IGES part that I have imported and converted to Sheet Metal. I do this semi-often and have not run into this problem.
To make this part "correct" for us, I needed to correct the inside and outside bend radius. I do this buy extruding a square through the current bend. Then cutting out the inside. Then adding our preferred radius with the fillet tool. I do this all before using the Convert To Sheet Metal tool.
For some reason I can not get this one to work. Where am I going wrong here?