Corner radius widget not available on some corners..

I created a simple shape and edited it to my liking. Corner widgets were availabl;e on every corner and all was good. Then after a while of editing fills, and line strokes etc, the corner widget was simply not available on some corners (see pic)

How do I get the cornet widget back? its still there on most of the othewr corners but some of the corners just look like the pic. Is there some way to convert the corner back to having the widget?