I am trying to alter the name of a 'Double' field using the Alter Field tool in Pro 3.1.3.
I am getting the error message 001600 Failed to alter field name:

I cannot figure out why. Here is the settings on the tool:

There is no option for field length coming up, but the field I am trying to change is null for all values except for one, which has a value '1'. So it doesn't seem to be an issue with a mismatch in field length. Other than that, I'm stumped!
Any help much appreciated, thanks.