What causes this part to fail?
 

I bought this part 11/2/2020 and it has already failed. Hall sensor/speed sensor for cruise control. I did all the testing and checked wiring to the ecu, by pulling EVERYTHING out: dashboard, ecu, passenger foot well, etc. to test everything and all was good. I didn't think it would be this part because it wasn't that long ago that I replaced it and I don't see where it would receive much wear and tear, but when I put in another one from a spare vehicle cruise control was restored. Anyone know why or what is it in these that fail? Part still looks brand new.

back when those cars were new, it was just old age after 6-8 years and a bad solder joint on the big pin.

I have just about given up trying new ChiCom parts. They're trash. I have had pretty good luck buying used OEM parts.

That's a genuine MB part, but still failed after 2 years.