In addition, the motors to open and shut the doors would have to be accessible for repair and/or replacement. Even assuming an exceptionally low rate of failure, the motors would have to be accessible for routine maintenance and inspection , as well the inspections required for municipal codes and insurance safety inspections.
In short, while the doors could fail, that this failure would trap people behind those doors simply isn't possible.
Incorrectly regarded as goofs
This seems to be even more incongruous later in the film when The Gunslinger uses a rifle (a long distance weapon) to shoot and kill a park employee. Why would robots need to use or have rifles when the rifle are not supposed to injure or kill guests or park employees?