I am having some trouble with the "snap to grid" feature when drawing.

For example, I can't seem to easily draw a downward vertical arrow. When I
click on the starting side of the arrow and drag it down, the "grid" doesn't
always seem to be under where the arrow started (I'm expecting that my
initial dot snapped to a grid point, so more grid points should be directly
below it). The "arrow" end will snap to invisible grid "dots" on the left
and on the right, but not directly underneath.

Sometimes, it is like the system got tired of watching me snap around to
various grid points, so it shuts off the invisible grid (as if I were holding
the "alt" key; except, I'm not holding the "alt" key, so of course I'm not
expecting this). Other times, it seems to strongly prefer to connect to the
ends of other shapes.

Is this as complicated as it seems or am I not using this correctly?