Magnets not on grid lines?

When I try to take a line to a magnet on a box that is not on a grid line, if that magnet is on the l/h side of the box it works fine, but if on the r/h side it just won’t do it. What am I doing wrong?

Also, why can’t I actually put or add magnets to boxes which line up with the grid? The s/w seems determined to put them mid-point between the centre and end of the side of the box.

I am running the latest version btw, 6.0.5, if that helps?!