Can someone please open up the attached SLDPRT file, edit the 3d sketch called "Wireframe", and tell me why I can't merge these two points (or make them coincident)?

It gives me this error:

If I manually drag and drop the point onto the other one I get the little "concentric" icon and they seem to merge correctly.

Playing around I seemed to be able to make it happen when one endpoint of my line is coincident with two orthogonal planes, and I try to make the other endpoint coincident with a point that is also coincident with one of those two planes.

BTW as a best practice I try whenever possible to affix my sketch entities to other sketch entities rather than ephemeral model geometry.  In this case, although the Property Manager fails above it does seem to work if you attach things to the equivalent edge and vertex geometry.  But I'd rather avoid doing that (to help make rebuilds more resilient to my changes).

I'm using Solidworks Premium 2017 x64 SP3.