Why have the copper pipes in my air conditioning started to leak?
Has anyone ever heard of actual pipes being faulty ?

My house was built, to a very good standard, 12 years ago. It had not been occupied before I purchased it.

The home was pre-piped for air conditioning. This year, three separate a/c systems (9 rooms) were installed.

One set fails repeatedly, losing gas. The installer tells me the old copper pipes for 2 bedrooms a ( 2+1 ) are faulty and need to be replaced. Has anyone ever found this before ? What steps should I take ?
Thank you for your guidance. I dont want to unnecessary waste more money and effort !