@VladimirPalffy and others,
I finally fixed it by adding a cut-revolve in the problematic corner...
I see that you fixed it below, but I meant add the round to the solid before it's converted to sheet metal, not before the conversion feature.
I have tried adding rounds to the solid (before the first shell, and after the first shell), but I still could not convert it (see my reply on the first page).
Adding a round to that edge also creates problems with the "bottom inner flange".
Thanks for the suggestion though!