The following behavior is simple to re-do on the default cube:
1. In edit mode, perform a knife cut through the cube. Anywhere, nothing special.
2. If you rotate the view during the cut (before hitting Enter/Spacebar to accept), the purple line will appear in a different location every time you rotate.
Attached is a screenshot (don't know how useful that is, since it's view-dependent).
Expected behavior would be to have the purple line come from the last edge-intersection (red dot), perhaps?
Thanks for your time.