I have just now noticed this in the Return to St. Vith scenario. The reinforcements for Day 2 have arrived as of a couple of hours ago, and I gave move orders to 10th Armored Infantry and 8th Tank Battalions (if I recall) to move them closer to the action, and a while later got a notification that both move orders "failed" to be executed, for no reason that I can see. So, I set them again, and when I looked at the order for the 10th I noticed that its estimated start time was advancing along with the clock, so it will seemingly never be executed.