When i use mastagger or change properties of file in foobar2000 everything seems to be ok but, tags were changed with proper data but...
I use MP3 player with tags support and i see only "EXĐ" on LCD screen and no info about album name or artist.
I search source of file and find that the tags code have two APETAGEXĐ fields and then proper TAG field. In each of theese fields i saw proper artist, album and other inserted data.
I don't know if it is bug but when i used other tagging method like Windows->Property of file or ID3-TagIT in source file i found only one TAG field and everything was ok on MP3 player.
Everything i mentioned above is about ID3v1 ( i think :) ), and MP3 files.

Sounds like buggy software to me.

I don't know if i am right but i think that my bug was fault of using APE tagging in playback/input/standard inputs. And it isn't correctly read by MP3 player i use ( RioVolt SP-250 ).
Only question is why APE tagging ( + ID3v1 ) is default in foobar. Can sb answer this ?
And sorry for bothering because this isn't bug exactly ( i think ).

It's the default since it's the best tagging format there is