I think it’s an issue of tolerance. They should be using gauges to test the fit, because hotel keycards can vary in thickness. Gauges are stupid cheap compared to the cost of the plane. It’s evidence of cost-cutting bullshit.
Same with using dish soap as a lubricant. It’s the wrong material for the job. Soap leaves a residue, and dissolves other lubricants. If there’s supposed to be lubricant in the door, the soap is a bad choice. If there isn’t supposed to be a lubricant in the door, then soap is a bad choice. It’s like Schrodinger’s lubricant. You won’t know if it’s a problem until it’s a problem.
No manufacturing process or material design is perfect. You get as close as possible, and then QA catches the mistakes.
For Boeing, it sounds like they didn’t try very hard to perfect their processes, and then didn’t bother with QA.