I don't think so....IF they mention it. If the doors just light up and open because the producers feel like it and no mention is ever made that the contestant really lost, then yeah, it's "rigged."
There was an episode of British PiR with....whoever came between Leslie Crowther and Bruce Forsythe.....where the host just felt like giving away the trip(?) and so the contestant got the prize even though she lost the dice game. Because it happened due to the host's saying so, it's not rigged, but if they changed the price of the thing on the spot, then yeah, rigged.