Whats the actual car speed? Make sure your valve is adjusted properly. You may be actually overspeeding. If necessary adjust down empty below contract so down fulls a little over contract, if it's an unregulated valve.

Once your sure your actual speed is what it should be, if your still getting overspeed faults, raise your contract/s1 speed higher. Your car only goes 2 speeds. But tell the controller contract is higher so it allows it to run without tripping that fault.

I've only seen one car that I had to do this on. It was running the right speed but the selector feedback was all over the place.