Check this video from 1:02:13 forward:    You'll see Allison Sanders planning movement and a shot preview where she can fire an aimed shot against the wraith, but when she commits the action and turns 180 a new wraith is spotted. After that, the unit no longer has enough TU's to commit the planned action. Also the FoW is temporarily not updated at the monent the new unit is revealed. Sorry, no saves for this one  as I just happened to see this video (not mine)