Door leaks

I purchased 2 replacement patio doors for $8200. After installation one of the doors leaks badly. Installer returned and said the door was installed properly and my gutters were the issue. The gutters have been in place for years and the original door did not leak for the 45 years it was in place. I engaged both a roofer and a local gutter company for advice on needed repairs. The roof and gutters are operating as expected. The only "new" variable here is the door.