Here was the problem, which also applied to Party Buffalo: I was using the raw disk size, and not the actual size that the Xbox uses from the security sector. So, for some disks, the size of the file allocation table would be off by +- (around)0×3000, give or take, which would then make the data region off the Data partition off by that amount as well, therefore giving the user bad (just random) filenames and other weird stuff happening.
Party Buffalo Drive Explorer 2.0.1.0 2017-02-07
Party Buffalo Drive Explorer 2.0.1.0