DSF Files - cannot assign tags to a large file

When tagging a dsf file, is there a file size limit? At least I have the impression...
I am using Mp3tag. I am not able to assign tags to the song "04 - Allman Brothers Band - Mountain Jam" (Album: Allman Brothers - Eat a Peach). I think that´s one of the longest track I have: Playtime: ca. 33 Min. Filesize is 1.33GB

Thanks in advance

What are the symptoms (besides that the modifications do not get written)?
If you get the message that the file is locked for writing, close WMP and Windows Explorer and try again.