Pivot table showing a person's name as a number

I have a pivot table for a large range of data showing people's names and the total number of hours allocated against relevant pay codes for data entry purposes. Randomly, upon refreshing the pivot table one day, one person's name displays as the number 52.

If I go back into the range and edit the person's name to any variation e.g., rename them Bob, add a space after their name etc., and refresh the table, the name appears as it should in the list. Any ideas what is causing this issue?