but that file is never in the file groups to start with? How did it get there? Did you put it there for some reason?
If you have SDMCFG.INI in your old 5.1.7 client file set, make sure that you have another copy in 5.2.x client file set.
Pay attention to file object ID's and revisions. Make sure that file in 5.2.x client file set has higher ID and revision. You can achieve that efect by making numerous file "export" and "update" operations.
you can increment a file revision just by pressing the "apply" button - but, I don't see how this helps? If you add a new file, it's a new file (object) - so why would the revision number compared to the original file (a completely different object) matter in the least?