As in title.
After saving a tag to MP3 file its duration as shown in Media Player Classic and portable player Sansa View is increased by 5 s. Foobar2000 is not affected.
I'm able to fix the problem with help of tool Vbrfix 1(beta) H+Moonbase-1
Below is link to 7z archive that contains two example file, one before, other after saving tag.
This is encrypted archive. Password is "aaa".
Mp3tag 26.4a (but I have that problem with earlier versions too).