CANT CREATE FINAL EDGE FLANGE FOR BOX

Hello,

I am trying to create and edge flange, however i keep getting an error that this is not possible.

The adjacent flanges are all 90-90, however the flange I am trying to create is 85-95

any idea why i can't create this flange?

Is there a different way of creating mitred flanges where one has a different angle to the rest of the folds?

Thanks

SolidworksSheet Metal