...Snoopy, did you eliminate the numbers completely when you renamed them?...
Yes,
in the first step I removed them completely ( using "SpeedCommander"-Software from PC ).
Then I renamed them with "new" numbers.
e.g. "[113]WALZER.SRG" is now "[046]WALZER.SRG"
The renumbered files I moved via USB-connection to the "/Registrations/Single" folder.