Shelley's black eye

I don't know why but Shelley's right eye, on the messed up side of her face, changes position from time to time. I guess the make up people didn't use a template and didn't always make it the same.

For example, in season 3 episode 2 when Shelley is in the snow covered graveyard at the grave of Prycilla, her big black eye is on the same level as her other eye, but at other times in the series it is lower than the normal looking eye. Sometimes it is only slightly lower, sometimes it is very much lower. Sometimes the top of the big eye is below the bottom of the normal eye.

I never heard Price or anyone else in the show explain this, or mention it at all. I don't think it is part of the story, just a variance by the make-up artists.