Artist name stuck in upper case letters

Hello everyone, I'm dealing with an odd situation here (FLAC file). The tracks of the album are all in upper case letters. (Greek). I change all the fields to lower case automatically or manually using mp3tag even foobar2000 but when I send them to my phone (Samsung music player) the artist name still appears in upper case while the ALBUMARTIST field appears in lower case. The tags in the photo are: Artist / Album artist / title / album
NOTE: The language is greek. When I insert a completely different artist name, the changes are executed properly.

So what do the fields look like in MP3tag?
Are they still in the preferred case?

In the mp3tag the field is in lower case.

Then it looks to me like a special implementation on the Samsung device.

There is a kind of autocorrect that appears when I try to convert to lower case. The other scenario in my mind is that the creator of the tags doesn't allow any changes to that field because this also happens in sone other flac files.

Where is that autocorrect? In Mp3tag? In the samsung device?

Either a file is locked completely or not. It is not possible to lock individual fields, esp. those very common ones.

There maybe an internal database in the device that does not update if there are only changes in upper or lower case.
Make a test with a file with 2 different file-names of the same file.

In the mp3tag programm

I suspect that but it should happen to all the fields not the artist name right?

This is getting more and more confusing.
Could you sum up where you see the behaviour that you do not want to see?

Does MP3tag change the case the way you want it?
Does MP3tag still show the correct case when you reopen the file?
Does the other device show the correct case?
Does the other device only show the correct case for some files?

-> The flac file when extracted has all the fields in upper case.
-> I open it with mp3tag.
-> I type every field (including ARTIST/ALBUM ARTIST) in lower case
-> while typing the autocorrector appears.
-> When I reach for the tones (ή ό ά in greek) the autocorrector dissapears.
-> I click save
-> I open my device
-> The artist name appears in upper case
-> I change the ARTIST name from Παντελίδης to a completely another name (ex. Papadopoulos)
-> Now the artist name appears in lower case

When you start editing in MP3Tag do you see the content for all fields including ALBUMARTIST?
The correct name of the tag-field in MP3Tag is ALBUMARTIST (not Album Artist).
Maybe you just create a new field "Album Artist" in MP3Tag.
Have a look in the extended tag-view (press "ALT+t) whether there are 2 tag-fields after the changes you made, one called ALBUMARTIST and one called ALBUM ARTIST.

Have also a look in the opened extended tag view at the upper infoemation line which tells you what kind of tags you have.
Does the same happen if you use MP3s instead of FLACs? (FLAC (FLAC) or smomething else?)

What do you mean by "extracted"? Do you rip the files from a CD yourself or do you get them already as flac-files with the tags in it?
If you create them yourself, how do you do that?

That is not an autocorrector but an autocompleter which shall help you to avoid unnecesary typing. You can enable or disable the autocompleter in Tools -> Options -> General.
The complter has nothing to do with your problem as long as you do not accecpt the completion (in capital letters) and change the field yourself.

I download them with utorrent and they are compressed. So I extract them using winrar and then begin the whole process. Yes they already have tags in them

I use the bar at the left in the mp3tag I don't go to extended tags etc. So there is no chance for spelling mistakes (if I made some in the answers above) In the mp3s everything is fine

I've also noticed that in the other flacs with the same issues when I right click and go to properties, a "BAND" field appears with artist's name in capital. Does this explain anything?

It does not matter what you use, just have a look in the extended tag-view which tag-fields with which content are listed there. In the extended tag-view all tag-fields that are embedded in your files are listed. In the normal tag-panel only tag-fields that are defined for this location on default or by yourself are listed. So to know which tag-fields are really there you have to mark a file press ALT+t.

Have a look here:

Thanks for the suggestion, I'll give it a try and come up with the results as soon as I can

So I tried a couple of solutions. I checked the alt+t and still everything seemed fine. I created a new field "BAND" wrote the artist's name and saved it. I opened it in samsung music and AGAIN, the upper case was there. So, I tried the same process with an mp3 file which used to be ok. Aaaaand bingo! The upper case had been transfered to it too, and all the files (songs) having the same name artist (flacs and mp3s). So, to my eyes, the whole issue is a glitch of the samsung music app.