Nothing seems different in 5.1 and 5.2 (may be minor fixes).
As per the foxfix doc the stealth mode automatically tracks each access to dbf file. This helps in using the dataenv and minor modification to old projects where changing all open files is difficult.

1. You are using a function to open each file.
2. There is no call to stealth function in th routine.

As far as I have tried the foxfix does detect the file corruption but does not fix it in exe running stand alone but does fix it when run from IDE.

Rajesh