Yellow Square, what does it mean?

Hi folks,

I've come across something I've never encountered before and cannot seem to find anything related to it by searching the forum or by searching my help files. Whilst working within a sketch I have created a closed contour which consists of a mixture of arcs, splines and lines. I had this in a fully defined state and then offset the contour outwards by 0.8mm (it's a very small part) and I ended up with this weird little yellow box at two of my sketch intersections.

Two thirds of the outer offset is fully defined and these lines are not. Could this 'Yellow Box' be a symbol for some sort of crunch point because of the intersecting lines compression as they were offset? I can't actually click the Yellow Box to see if it gives any further warning or help. Unfortunately, I can't attach the file as it is too large.

Has anybody seen this before that could shed some light?

Dave.

SolidworksSketching