[Twan]

My map is a little too big and it seems in some cases problems occur with very long movement arrows. Sometimes the arrows never appear, or appears only if your screen is on the first province (but you don't see them on the destination). One or two times I even had a game crashing when drawing the longest arrows (I recommend to do a "save game and quit" and reload before doing the very long range movements, to be sure not to lose the other orders ; zooming out to see the two provinces also reduce arrow drawing problems).

...but I never had an impossible movement, so I don't know for your problem (which provinces are concerned ?).