LOTS Of the songs uploaded do not show tags on GPM for cover art (art is only thing I looked at so far as it's easy to notice the absence). Here is an example:

In the above you can see the cloud symbol, so MM5 knows it uploaded it. And it has a cover art tag:

But here is what GPM has:

So is this what @Barry4679 has mentioned (in https://www.mediamonkey.com/forum/viewt ... 30&t=94858), where GPM is storing someone else's copy and not mine? Or is GPM not uploading the track with tags intact?
I downloaded the track from GPM manually, and ran a different program to look at the tags (Tagscanner 6.0.35), and there is no cover art. I ran the same program on the FLAC track inside of my MM5 music library and the JPEG tag is there in the image (not separate in the folder as a file).
So either Google stripped it on arrival, replaced the track entirely with one it had, or MM5 did not include the tag during the FLAC -> MP3 conversion.
Here's a side by side display of the FLAC (on the right) from MM5's library, and the MP3 that I downloaded after MM5 uploaded to GPM. Notice the track tag, disk tag, and Year are also different.

It really looks like GPM replaced the track once it reached Google? I could see MM5 losing a tag, but it seems unlikely it is changing a tag in subtle ways like those others.
Unless....
Unless...
I noticed that GPM has a "Trash" where it appears to keep the last deleted copies.
Could it be that if you upload song X, and it has a copy in trash, it replaces it from the trash instead of the upload? Not sure if I am suggesting that GPM is doing that, or MM5 is doing that.
I have been repeatedly testing this by deleting all the songs from GPM. I have not been clearing the trash. I have also been tagging my library as I went. It is completely possible that this album at one point had different tags. Maybe it landed in TRASH and has just been recovered from it on each subsequent upload?
I just did a "permanent delete" on all trash. I will let MM5 finish, and see if subsequently uploaded songs have the same problem. I will also delete this one (permanently this time) and sync again and see what happens. I think it is a long shot but possible, I guess.
But something is wrong.