You surely have a sensor problem.
Diagnosing which one isn't so easy. Your sensors are working most of the time or you would be getting the light all the time. Because the car wheels travel at different speeds when cornering or going over bumps the controller has to decide the difference between such activity and poor signals.
We use the Bosch tester and when used according to design these problems couldn't be decided. Bosch and MB say to test each sensor by turning the wheel while on the lift. For years we never found the sensors using this method. Finally we tried driving the car at 2-3 mph (holding constant speed) while switching from sensor to sensor. By doing this one can see the differences. Doing one wheel at a time the differences in wheel speed caused greater differences than the problems did.
These tests could be done with a voltmeter and/or scope. But the problem will be switching from one to the other for comparison under similar circumstances.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician