Try opening the .dbf file in Excel or other program that supports opening the .dbf format.
Once opened in Excel you should be able to view the file, delete any “bad data”, and resave to a new name (with the .dbf extension).
Also possible to create a new table with the structure of the old table, append records from the old to the new. May salvage records until the corruption is encountered.
Also this issue is discussed on these sites: http://www.filerepairforum.com/forum/databases/databases-aa/dbase-iv-clipper-foxpro
https://social.msdn.microsoft.com/Forums/en-US/614c63be-0b75-4620-8aaf-2fda28038bfb/how-to-fix-file-index-corruption?forum=visualfoxprogeneral