I believe there is a bug in the Move/Copy Command. Something has changed for the worse since SW2010:

When I use Move/Copy on a body and right-click on the center ball and choose 'Align to' a line that is NOT parallel to any of the major axes, the subsequent move works in mysterious ways. Dragging an arrow in a single direction will produce a movement in a composite direction - often opposite of the direction I drag the arrow. What on earth is going on?

SW2010 was fine

I don't remember seeing the issue in SW2011, SW2012 or SW2013 (educational versions) but I could be wrong.

SW2014 and SW2015 has this weird behaviour.

The fastest way to replicate the issue is to draw a 3-point rectangle at a random angle, extrude to a body, use Move/Copy and align to any edge and try to move the body in the expected direction....!