Mystery solved! This is not a camera or sensor issue, it’s caused by the mirror. Thank you @WeakInteraction and @tr_babb for teaching me something new! In the US, driver side mirrors are flat for more precise depth perception and the passenger side mirror is convex for a wider field of view. My rental car in Argentina has convex mirrors on both driver and passenger side which caused the focus discrepancy. When I was testing focus with my 50mm lens film camera from the passenger seat, it looked like perfect focus behind and within the driver side mirror, but I bet when I get my film developed the focus will be off. Tested again from the driver side and the mirror is indeed convex. The rear view mirror is still pretty flat, distant scene in focus within and behind the mirror.