While converting database of a file, there's a migration problem in Flex2SQL. The error seems to indicate a problem creating the inverse key for overlap field.
This issue happens because a bug in DataFlex. It shouldn't allow an OVERLAP field to be a case insensitive segment. You can set this attribute when creating the new index. Next time you open the file with DFFILE you won't allowed to touch on this attribute.
In Database Builder you get an "invalid attribute" error message if you try to set an overlap field as a case-insensitive index segment. So this index should be recreated without setting this overlap segment as case-insensitive.