Different Folder Cover

Hi everyone, I'm using mp3Tag to sort the folders of my albums that I have digitized. Everything is going well.
But sometimes the folders that contain the files, mp3 or others, (just completed individually with the covers) appear with the single cover, others with 2 identical covers, others with a cover image plus the icon of the program with which it is associated the file, others with a small cover.
Could anyone explain to me why? So that I can solve the problem of having a single cover per folder.
My pc has 64-bit windows 10.
Thanks so much!!

folder_cover_example Here are the pictures of the folders:

I would check these folders:
have you got different media files in the folders?
Do all the files have the same embedded pictures or are they different? (I bet that Windows does not look at the contents of the pictures but simply evaluates dimensions and size)
Have you got a file called folder.jpg in the folder (you may have to set the option to see hidden files)?

Hi, each folder I'm creating contains only the same media files (e.g. 15 .mp3 or 15 .flac files).
Within the same folder, each multimedia file has the same image associated with it.Usually I use .jpg 600x600 pixels.
I always keep enabled the viewing hidden folders and files.
There is no folder.jpg file, usually if there is I delete it.

another system file could be thumbs.db.
I checked my folders for more than one picture in the "symbol" view and either there were not just more than one or if there were more, then it was clear that this came from several files with different embedded pictures or even exported pictures.

Hi, I seem to have solved it.
Hidden folders and files are displayed.
But I had activated the 'hide protected system files' box.
Once the flag was removed, the various ALBUMART, FOLDER AND THUMBS appeared immediately.
Now that I see them I delete them and finally I have my single covers in the folders!
Thank you so much for the help Ohrenkino!