WorldToScreenPoint conversion inconsistent

I've gotten the camera to follow my player pretty well. When the players position is past the half way height of the screen, the camera locks to the player. Otherwise the camera is locked to the player or at least that what is suppose to happen. As long as the character is ascending everything works great, when the player starts to fall everything gets a little glitchy.

Here is the code I am using to follow the player:

 void FixedUpdate (){
     float x = _xStart;
     float y = _yStart;
     Debug.Log (player.position.y);
     Vector3 pp = camera.WorldToScreenPoint(player.position);
     Debug.Log(pp.y);
     Debug.Log (pp.y > Screen.height/2);
     switch(WorldManager.GetGameState()){
         case GameState.LAUNCHED:
             //check if player is past mid screen before following
             x = pp.x > (Screen.width/2) ? player.position.x : _xStart;
             y = pp.y > (Screen.height/2) ? player.position.y : _yStart;
             break;
     }
     
     // Set the camera's position to the target position with the same z component.
     transform.position = new Vector3(x,y,transform.position.z);
 }

The state and all that is working fine. What I've noticed is pp.y is jumping up and down on the players decent. The logs display the following (obviously simplified):

 11.63518
 192.9192
 False
 11.48117
 633.3361
 True
 11.3255
 192.7765
 False
 11.1682
 619.8181
 True
 
 etc...

To me this points to there being a problem with camera.WorldToScreenPoint no converting the value properly? (which doesn't make sense to me) Can anyone see anything that I'm messing up. If you need any more info please ask.