When using the Merge Patrons tool, or any other KLAS function with a KLAS ID field, Find button, and Name display field, make sure that the patron's Name fills in before applying changes!
When you use the Find button, both the ID and Name fields will fill in. But if you type in the ID instead, you need to either Tab out of the field or click into a different one for KLAS to look up that ID and fill in the Name.
We are adding validation to the Patron Merge tool, and will add validation anywhere else we find that it is missing. But in the meantime, and to save yourself an error message once validation is in place: Always check that the Name field is filled in!