Fleeing alert is bound to queued animation, happens too late

Joshua has just supplied some stone to a ladder and started construction when suddenly he throws his arms up in the air in self defence against... nothing?  There's nothing nearby that would harm him?

Exhibit A: Joshua has the willies

Loading a save, I was able to see that Joshua was injured prior to his arrival at the ladder.  He stands right where the pokeshell is to pick up the stone.

Exhibit B: Josh takes a hit but there's no alert yet

Josh then climbs 48 tiles up the ladder, then 40 tiles left across some bumpy terrain before he starts construction work shown in Exhibit A.

It's about 26 seconds between the pokeshell taking a swipe and the alert appearing.

Exhibit C: Joshua seems very dedicated to his work.