That happened to me as well, but my mouse is good.
However, I don't think you need a double-click, I thought one clicks once and sees the path, and then the unit moves when you click again on the path? (Funny how I cannot remember it right now when it is not my turn.)
However, sometimes I click and nothing happens, no path is shown. Then I click again, and the stack immediately moves.
I guessed that this was due to bad internet connections or a busy server, so that the path display was just forgotten by the client somehow, but actually the client ought to be able to compute the path all on his own without server interaction until the command to move (into fog of war) is actually given?!
That said, an option to confirm each and every move might be too cumbersome - at least I would certainly not used it. However, a keyboard shortcut to cancel the move path would be very handy: my
current workaround when clicking inside the map to measure distances is to click the button for "cancel movement path" in any case first (i.e. regardless whether a path is shown) if I want to make sure that this stack surely remains still (e.g. Hero stacks close to the front, etc.)