We recently upgraded to GraphQL-Java 21.3 and are getting a new error: "Internal error: should never happen: Should have been validated before."

The error is cropping up on a mutation that looks something like this:

mutation foo { namespaceMutation(xyz...) { mutationFunc(input: {args: .....}) } }

our input looks something like
{
arg1: []
arg2: ID!
}

We only are seeing this error on inputs. I'm not sure why we are not getting the normal coerced null error.