SW2015 SP5

Occasionally, like in the snap below, I or a coworker have had a problem where a surface edge is unselectable.  We go back and recreate the surface offset/surface extrusion/ whatever, and all is well.  But then of course anything related to the offending surface that has to be recreated goes bonkers and needs fixed, which we work through.

Question, if you look at the attached snapshot, you will see all but 3 edges can be converted, but the 3 the arrows point to are unselectable...any thoughts, have you seen this?

Brian