Duplicate Search Merge Problem

I only recently noticed a problem in the Duplicate Search Merge feature which I cannot even get to repeat reliably. It happens when you choose the Start with Surname option and gives false results even though the surname chosen has been verified to have possible duplicates using exactly the same search criteria without the Start with Surname field completed.

When I do a Duplicate Search with the default criteria below on a particular file......

I get the following results –

When I now repeat the exercise on the same file but entering Gracey as the start surname as below.......

In this case RM shows a blank return with no possible matches as below. It's the same file and the operation was performed with the surname start directly after the original search?

 This feature works perfectly well everytime in RM3