Wrong song appearing one phone even if the right one appears on my PC

I don't know if someone already answered that, but I got an annoying bug.
Sometimes the cover of a song appears on my pc but on my phone it's a different one, that I have used before for another song.
For example, I got 2 albums from a french raper, so 2 different covers. I tried everything but each time the 2 albums have the same picture on my phone even if on my pc the right covers appears!
I tried adding the songs one by one, taking a picture from another URL, changing the cover again, but nothing is working even if I completely delete the picture that keeps appearing on the wrong song!
I really don't understand why tf it's happening and I'm fed up with that, if someone could help me it would be amazing.
Sorry for my bad grammar.

I hope this is not true and it is a rapper... no, just kidding.
What kind of files are we talking about? MP3? WAV? MP4?
First check if you really have embedded the pictures with a filter:
%_covers% MISSING
If no files show up: great.
If Mp3tag then shows the correct picture then it is most likely that the correct picture is also embedded in the file.
For the external device: you have to find a way to update the apparently existing database on that device.
If you have access to the file system, see if you have file called folder.jpg in the folder of the audio file - and delete it.
Yet, we had devices that access the internet on their own and try to find a cover...

Yep, MP3 files. I'll try.