SPI digital height gauge problems

I have an 18” spi height gauge, that I’m having problems with getting the lower 6” or so to read, it all works normally above that, but Once it hits a certain point it just goes to some random number and doesn’t move, I tried resetting the origin in the lower area and it just resets to zero, then doesn’t change until I hit about 6” then it starts reading, maybe the scale is cracked, but I thought I’d ask if anyone else has had a similar issue that they fixed, I don’t see any marks that could have caused the scale to crack, but who knows, my thoughts would be that even if it cracked at that point, shouldn’t I be able to get below and set the origin and work from the lower part?
Thanks