Hmmm. This was a bit of a CAD riddle the brief way you describe it.
After trying to think to what you refer, the only thing coming to mind is that you are not actually selecting right on the entity
but clicking right next to it somehow in a region of empty space. This indicates to progeCAD to begin a "selection window
", at which point it will then ask for "Opposite corner" to finish selection area. Does it look like an elastic selection box is appearing when progeCAD
asks for "Opposite corner"? (If not make sure PICKDRAG system variable is set to OFF, then the selection window will stretch until you select a second point for it)
To solve your problem I suggest simply a larger PICKBOX
aperture size for your cursor. Type PICKBOX and enter "6" for the value and try your fillet selections again. The effect of this change is making it easier for yourself to select directly on an entity and less likely to "miss" and click in empty space.
This would be our firsth thought after a couple of re-reads and bit of discussion, let us know.