Story view view issues

I'm sure this is an easy fix for someone but it's driving me nuts. Every time I go in and out of Story view my 'view/zoom' changes. One minute the individual slides are easy to view from Story view and the next they are pin size. I will open up a slide and do some work on it and when I go back into Story view the zoom has changed.  

Zoom/view on open of course = snap 70%.png

zoom/view after a slide edit = snap 70% 2.png (slightly smaller as you can't see the slide name in view)

zoom/view after another slide edit = 220%.png (didn't change the zoom)

zoom/view after another slide edit = 60%

HELP!!!!!!