I have an application based on graphql-java. In my case when I try to pass an argument with same name it will not fail and it works by keeping last value.
But according to graphql specification, duplicate field should not pass validation and throw a validation error.

https://spec.graphql.org/June2018/#sec-Input-Object-Field-Uniqueness