I find Windows Media Player (WMP) to not be a friendly app. It's goals didn't mesh with mine as it wanted to rename and move files by default. MSFT has improved WMP but lost me years ago as WMP changed and tossed out my content from time to time.
I went back to simpler players and simple collections without using WMP. Fast forward to today and your complaint only adds another reason to find something else.
I use the column 'Parental Rating' as a facility to code my music per dance, (Ballroom or Latin American) e.g. WZ (Waltz), TAN (Tango), RUM (Rumba, WC (West Coast Swing). If I am ripping a large amount of music, I code them all as UNSORTED till I have time to sit and work them out. I often have the problem that WMP will not allow me to edit this column!!!! Other days I can just start up the computer and it does it at my request. What setting must I alter / change to make this work permanently? Thanks.