I’ve had this exact same problem, haven’t found any solution I’m afraid.
I’ve tried re-encoding the ID3 tracknumber tag using just about every version and character encoding under the sun and gotten nowhere. It’s sorting either by filename or file modified time, I don’t recall.
I hope sandisk put out a fix for this soon, cos my shiny new clip jam is kinda useless at the moment. Shame, cos I’ve owned previous versions of the clip series and only had good things to say about them in the past.
the issue has been reported to sandisk support. they are looking into possible supporting ID3 track number sorting for Ogg files. ID3 tag track number is supported for the other supported file types so you can convert the files to one of the other supported file types and it will sort by track number.