Path ≠ line if you have a round arrow with an arrowhead as part of the path
If you have a "round" arrow with the arrowhead as part of the path, the path (in my screenshot: blue) is no longer the same as the shown line of the arrow (black).
This effect does not occur if the arrowhead is added to the path.
Rainer Klute shared this idea
For me, adding an arrowhead alters the arc to which it is added. This file is named ScissorProblem, because I thought the Scissor Tool was causing it. That may or may not be true. It happens when the arrowhead is placed at the tip of the path. The problem goes away if I select "Extend the arrow tip beyond the end of the path"