Spectre is a whiney b!tch and Cadence won't do anything
about that. It allows and requires you define a model once
and only once. Evidently tolerance of errors and redefinition
was just too difficult to code up. Strange, since they were
built by looting SPICE and CAD experts from their customers
who had witten much better user interfaces.
Anyway, the problem lies in your setup include-chain and
either this set of xjvar_ files is invoked by some earlier
include, or they are defining models with the same name
as an earlier include.
There's nothing for it but simple diligence.