When I try to copy sheets in a workbook to another sheet in the same workbook
I get the following error message:

A formula or sheet you want to move or copy contains the name 'aa', which
already exists on the destination worksheet.

This repeats many, many times until it ends with something like
'zzzzzzzzzzz'. How can I preclude this from happening? I don't have any
named ranges in the sheet/workbook that this occurs in. Has anyone seen this?