Problems with alphabetizing

I took the time to alphabetize my iTunes library by Artist Last Name (ie. Joel, Billy). I found that you have to go into the "Get Info" and also change this in the sort order. My problem is, from time to time the alphabetizing reverts back to default (ie. Billy Joel). When I go to "Get Info", the information is correct with the last name first. I click "OK" and it fixes the problem. This gets tiresome to click on "Get Info" then "OK" for the 200-300 songs this affects. It seems I have to do this about once every couple of months or so.

Why does this happen and is there a way to fix it?