axev was on a lot of older stuff. avex used to be known as axev up until like 1997 so I am not really sure why it persisted onto items past then but I don't think it was ever in 'error'. It's possible that they named their management division axev up until a certain point.
http://www.itmedia.co.jp/mobile/arti...2/news090.html
It was even still 'axev' in 2005. I think I remember seeing "AMG" sometime around 2008-2009.
They are all the same thing though.
axev = AMG (Avex Management) = AEI (Avex Entertainment Inc.)
http://www.4-traders.com/AVEX-GROUP-...roup-18440647/
I think it's got to do with some internal company-related mergers and demergers which resulted in some different names here and there.