I doubt it was a malfunction at the factory, they say it's a 1987 (it's indeed the 1986+ facelift) but the 242 was discontinued in 1984 so they wouldn't have a two-door side just laying around...

I have seen a three-door Amazon as well. This one is said to have been comissioned by the buyer from a four-door. They don't know if it was made by Volvo or by a coach builder. It is said that it was used as a school taxi and they didn't want the kids to run out in the street, hence the two doors on the right and one on the left.

https://youtu.be/KIZAxFwir8E?si=MoCZLQN0GAfAmJ-J&t=108