Was it 5 rounds simultaneously or 5 rounds in succession? A 32 degree error is about a 566 mil error! That's huge. If 5 rounds impacted at the same time I'd say that whatever element fired was not layed properly onto an aiming reference. If it was 5 successive rounds that means the gunner likely put in the wrong number in the azimuth counter scale OR wasn't laid onto an aiming reference properly.
If they were only 3 klicks out, the discrepency would have been VERY noticable on the gunline. The only way it would not have been is if the Firebase had just a few guns at the apexes of the base and only one tube was responding to the fire mission.
Of course, the observer could have given a bad grid (usually either off by one grid square or called on their own position because they lost track of which grid they were using)
Whoever called it made it a fire for effect mission. Otherwise, the damage could have been nullified with the adjusting rounds where only 1 round would have impacted where it wasn't supposed to...instead of 5.
I would imagine these were the most likely scenerious for this type of mistake to happen.