Photoshop elements 15 image disappears whist editing

Hi 

New to this , Ive had Photoshop elements for a few years now on my macbook air completely problem free , but recently its started to play up , when you have the image for editing its ok then as you adjust the levels for instance the image disappears untill you stop moving the slider when it reappears , this happens on all adjustments (sharpness,lighting,colour etc) 

Please help 

Noel