Editing in Animator removes Player tag

I have a player character which is labelled with the 'Player' tag. The game runs smoothly (is able to locate and assign variables through the FindTag function) until I edit the player character animation. When I make edits through the Animator the game object will continue to hold the 'Player' tag but the scripts will no longer be able to find it. Eventually I will get a NullReferenceException Error. The only solution I have found is to restart Unity. I have tried deleting the 'Tag Manager' file but this is no more effective than simply restarting Unity. Any ideas? I am absolutely stumped.