Crank sensors keep failing

Replaced 3 crank sensors in six years (cheap eBay £25ish) then bought a facet sensor that failed after 2 years on Monday fitted my new spare that died Wednesday after 70 miles I have now fitted my used spare spare.
Are the aftermarket one's really that bad or could there be another reason why they keep failing?
Golf 2.0 96 aag

 

A lot of fakes on the Web.

 

Well my replacement Hella sensor just failed after 4 days either I'm unlucky or its killing the sensors any chance I have a problem?.

 

Was it off ebay or from a store?

 

This one came from a local motor parts suppliers there going to exchange it under warranty.