Sorting glitch/problem

[redged]

Hello

I have 1 artist that is sorting by last name first and cannot understand why. Everything else sorts correctly(how I like) eg Frank Zappa is under F, The Beatles are under B etc, but for some reason Ryan Adams is showing under A?

I have tried deleting all tags and then re-entereing them but it is still happening. I have over 1500 albums which are all sorting correctly except these 2???

Thanks in advance for any help given.

Kind regards

Ged

Update - I have inserted the following in my sorting.txt which has fixed the problem, but would be nice to understand why it was happening in the first place.

@ARTIST=Ryan Adams
+ARTISTSORT=Ryan Adams