It was already suggested that it would happen if the same filename is used in multiple file-sets that are assigned to machine. Inspect them first. Do not delete any files, unless you know their purpose and impact on particular systems. Test first.
Yes you´re right. Should have investigated this myself more carefull before.
I find in my file group "EEPC51 OPTION: Update MBR for EEPC Comp..." and also "EEPC51 OPTION: Update MBR for Safeboot Comp..."
Same thing with "EEPC51 OPTION: Exclude Sector 59 for NEC Comp..." This *.srg file you also find in "EEPC51 OPTION: EE 5.1.9 Client Files"
Many thanks for your quick answer though!