Is the database hosted?
Try sorting the records on the host machine or if hosting from Server, take it down off the server, open in FileMaker Pro, show all records, Sort the records and then put the file back up on the server.
It is hosted by FM server on a mac mini server.
Having removed db from Fm server, I should open Original DB via remote connection/local connection, resort then re upload to FM server??
I don't know if that will work, but that's what I am suggesting that you try.