I don't know why this worked but I edited ANOTHER DIFFERENT shipment method range for the same zone that throws the error and then I edited the one that was giving me problems before and it didn't throw the error 🤷♂️
But only worked for one zone.
I'm going to try delete all ranges and start again since it won't let me delete the carrier.
Edit: I deleted all the ranges and started again and now doesn't throw the error.