For various reasons, an sdlxliff file may become corrupt. However, Studio doesn't seem to notice that itself. I've seen that Studio will happily create a return package with an invalid sdlxliff file (with invalid syntax), which is then only detected, for example, when trying to import that return package into WorldServer.
Studio will even generate a target file from the invalid sdlxliff (using Save Target As), which is then also invalid.

In my opinion, Studio should at least do an XML syntax check whenever it writes an sdlxliff file or creates a return package (or at least have an option to do that). The earlier any corruption is detected, the better, so corrective action can be taken before the problem gets worse. With "syntax check" I mean just checking the XML structure, not checking against the schema because the schema is often not available.