Hello, and thank you!
I am producing mp3 from webinars, where I record the audio track and produce individual mp3s for each training session.
Each mp3 should have a different piece of album art associated with it.
If I have four mp3s, I use four different pieces of art- per the request of the presenter of the webinar.)
Use of this wonderful product (thanks!) has made this an easy process to produce such mp3s 
I take care to individually handle each mp3, coupling it to a given piece of art, step by step.
I am not inadvertently doing a batch process at this step.
When I then view the tagged MP3s in my directory, I see that each mp3 has its correct album art image - terrific!
However, I have noticed that the album art gets lost when I load the mp3s to a cloud service (Sharefile) or download the files to my phone (LG Android phone).
As such- the album art for (seemingly) the first MP3 loaded is populated across the other three mp3s. So- on download- I have four mp3s, all with the same album art (whereas they all had their own individual album art on original production). I'm losing the album art for 3 of the 4 mp3s, and the single piece of album art is being populated across all four MP3s.
What am I doing wrong?
I SO appreciate any kind considerations and insights!
Always the best to you!
KJK