Defender 90 door key snapped again

Over the last 6 years I have replaced 6 door keys They last about a year. All snap at exactly the same place on the key even though I am extremely gentle with the keys. Latest key snapped yesterday as I was unlocking the diesel cap!! Has anyone else had this problem? or suggest a solution.

Have you used the same place to cut the keys each time? - could be that they have cheap low quality blanks