Spurious click generated ~100 pixels above (north) of pointer

In some circumstances, when the user clicks, a spurious pixel will be created ~100 pixels above (north) of the pointer position.

Although originally this appeared to only be with the paintbrush, on a single occasion it has been seen with the flood-fill magic wand.

This will repeatedly happen until some combination of + swapping colour + swapping tool occurs + swapping back occurs to reset the state.