The brief
The Golf had the ABS warning light steady on the dash and the traction control symbol flashing whenever the road was damp. That pattern points straight at the wheel speed sensor circuit: the ABS and traction control both need a clean speed signal from each wheel, and when one of those signals goes flaky, both systems light up and the traction control kicks in at the wrong moments.
Each wheel has a small sensor at the hub that reads how fast it's turning. When one fails or starts reading intermittent, the controller doesn't know what that wheel is doing, so it warns and pulls the systems offline rather than acting on bad data.
The diagnosis
The scan tool pulled a stored fault for the right front wheel speed sensor reading intermittent, range and performance out of spec. The resistance on the harness checked within spec, so it wasn't a wiring fault feeding it, it was the sensor itself failing.
That's a replacement, harness left alone. A flaky sensor only gets flakier, and an ABS warning that's been on a while trains you to ignore it, which you don't want with the brakes.
The work
The front of the car was lifted, the wheel came off, and the failed sensor at the hub was replaced with a new VAG-spec unit, the lead routed clear of the brake line so it can't chafe.
Then the stored fault was cleared and the ABS module recalibrated, and a road test, including some damp-road braking, confirmed it.
The scan came back clean afterwards with nothing returning.
The outcome
The ABS warning light is off, the traction control stays quiet on damp roads, and no fault came back over the road test.
The Golf went home with the braking system reading clean. A wheel speed sensor is a small part with an outsized effect, it takes ABS and traction control offline when it acts up, so replacing the failed one and recalibrating means the safety systems are back doing their job rather than sulking on bad data.