@Choco
As it's been shown that your device's region 41 doesn't delete or erase successfully (and therefore likely cannot be written to either) it's of more concern that there's other problematic data rather than some outdated data related to earlier maps.

Does GarminDevice.xml properly update after each boot-cycle? Try moving it manually to a safe location on your PC and then boot the device to check it's properly re-created and compare the two files if it is. If it's not recreated properly on boot then the device certainly can't even read data in region 41.

About Audible, there are only a couple of short sample books and a Welcome audio in that folder, and you'd need to add books in .AAX file format to listen to more. Nobody ever seemed to use it much to listen to audio books on Garmin devices anyway in my experience but if you want the original files here's the zipped folder: [Only registered and activated users can see links. ]

BTW, the .SUM extension is indicative of checksum files and they're not really needed even for current files so either can be deleted safely or just left there - even for old unused removed files - they won't harm anything.