I give a unit several orders and move on to manage another part of the game and then I'll hear a sound and the unit has stopped and did not complete the orders. This happens when giving move orders, build orders, etc. It happens with the commander as well as all other units. Why do my units keep stopping and not completing orders it is very frustrating to have to go back and re-queue orders or follow units around so I can keep giving them move orders, because the stop part way to where I told them to go.
Do you use WASD to move around the camera? By default 'S' is bound to cancel order, so bind it to something else.