Open the files.xml file and then one can find the 'humanly recognizable' file name along with the associated contenthash file name and thus be able to locate in the files directories that should contain the contenthash file. (confusing, isn't it? :\) Does the 'humanly recognizable' file name have any characters that are allowed in Mac (if that's what you use) but NOT necessarily allowed from server. Case in point: can name a file on a Mac using a '/' character in the file name. On a Linux server that could cause some issues as '/' is a designator for directories - translate path. So it's those sort of characters one is looking for.
See you are using a Mac to browse the extracted backup .mbz contents so get info on any of the contenthash file names to get information. If you desire to see if it's corrupted, copy the contenthash file into a test directory somewhere on your system, then using the info found in files.xml rename that file back to it's humanly recognizable name (include the filename extension). If your Mac can open, it should provide an icon, etc.. And, if you have an app that will open the file, doubling clicking on the renamed file should launch whatever and play/show, etc..
'spirit of sharing', Ken