Well I can understand young horses having a period of greeness due to being unexperienced, but for an older horse that is strange.
Pacifiers are there for a reason, so I would imagine it is a matter of finding out what is causing the horse to be un-settled and to pacify the cause. Head stable lad can sometimes give you an indication to the cause although it is fairly rare.
Blinkers are applied over the horses eyes if they are easily distracted, which could be the unsettled message you are seeing, therefore enabling the horse to remain focused. It maybe that a horse likes to lead from the front and when it isn't it becomes distracted and sulks. There could be other reasons such as the horse is just not really a racehorse
Also the horse 'would not settle' could be related to the paddock reading before the race. If your horse is more agitated before a race than normal which is denoted by the up red arrows this coudl cause the horse to perform poorly and appear unsettled. Generally hiring a paddock/start staff member would make this event un-common fortunately.