contamination - be it pushing back old fluid into the modulator during brake pad replacement or contaminated fluid(with petroleum products or dirt) can ruin an ABS modulator. Today’s cars with tight HMI/ADAS integration with the ABS/ESP system, if the modulator is bad, the car might not work as intended.
Has anyone else replaced the brake pads on your car?
@Trav taught me something here a while ago - crack the bleeder screw before pushing the caliper piston back home. That way, you prevent any particles from entering the ABS modulator. Yes, you will need to bleed your brakes afterwards but brake fluid is cheap compared to a new modulator.