The application looks for everything which breaks one or more specifications or conventions.

Yate will fix the types of errors displayed in your post as a matter of course whenever it saves a file. iTunes also happens to do well when avoiding container errors.

Many file types such as AIFF which are based on chunk container formats actually store the size of the data within the file. In both the above cases the stored file data size does not reflect the actual size of the file. Yate, as I would hope most other applications, ignores the contained file size because it is so often incorrect and can be wrong in either direction. Too large or too small.

The trailing nils errors is not strictly against spec as the spec says that all characters after and including a nil should be ignored. However, we've seen applications which mess up the display if the nils are present. Perhaps this one should be an option.

Other errors such as padding before the audio stream in mp3 files mess up a lot of utilities. There is also at least one well known streaming engine which messes up on virtually any error which is out of spec. If any of the files identified the presence of control characters, the files should be fixed.

The fact that the files were purchased does not by any means imply that the files are correctly formed. There is at least one large vendor out there who is producing files with malformed ID3 frames. This results in URL fields which will not load the URL and other frames which most taggers are forced to ignore. When we find these issues, we work around them and fix them when saving the files.

The general rule of thumb can be: "if it plays okay and displays okay .... ignore it".