This has been an ongoing "philosophers stone" in the repair community for a long time. Hard platens are the result of the rubber losing its moisture, there's virtually no way to fix that long term. Brake fluid, rubber renew, even the wintergreen oil trick only temporarily soften platens/feeds. They will absolutely go back to their former state after a time. (1-2 months) You can sand the exterior and clean with organic solvents to restore grip and improve the original platen, but recovery is really the only long term fix. *There's a ton of back and forth about the sanding method, particularly from the old timers being salty about it. But I have seen HUNDREDS of old platens in machines that have absolutely been sanded by repair folks back in the day, so there's definitely value in the process.