ABS-problem, velocity spikes. Graph of velocity during test drive

S80 2001, 2.4t. Scanning with VCT2000 (volvo can bus interface) and VADIS software.
There are spikes on the speed signal. The speed of the car is constant. The needle in the driver instrument also jumps/jerks.

Wheel Front left

Wheel Front right

Looks like the front right ABS sensor is not telling the truth :-)

Yes, indeed, after replacing the ABS-ring containing the teeth that the ABS-sensor reads,the speed curve is now smooth and STC doesn't kick in.
Here are some pictures of the old ABS-ring.