How does the cat trigger a check engine light - are there sensors in the exhaust system beyond the cat?

Could the sensor be bad?

When techs address a code, there is often a decision tree that they follow - some times the issue is upstream of the item that sets the code.

Has your engine been tuned up lately?

Ignition parts and air cleaner?

I would do (or have done) a tune up and then have a dealer tech check the car.

At least, you would have less risk for the new cat.

Perhaps the short life of some replacement cats are shortened by older cars that have other issues.