No fix is required; the system is functioning as designed. This action is not supported in all Gaia and SecurePlatform versions - it is not possible to add a route to the link-local address on the Check Point side.
Use a global IPv6 address in the Check Point side and configure all the routes in the "router" side that it will be a 3rd party.
This solution has been verified for the specific scenario, described by the combination of Product, Version and Symptoms. It may not work in other scenarios.