I have a number of lines forming corners in a sketch that I'd like to add sketch fillets to. The lines are dimensioned and sometimes when I apply the sketch fillet the dimensions are maintained with witness lines added that continue to their projected intersection point. However sometimes this isn't the case and the dimensions are deleted. I have "keep Constrained Corners" checked but that doesn't seem to make a difference. How does one select the corner to fillet while keeping any existing dimensions?

Thanks