Zoom in/ out bug on STB PRO 20

Hello
Weird things for the zoom in and out which is very lilimited OR doesn’t work at all.
Whatever I use to do it (Icon, shortcuts, even 2 fingers on the track pad of my Mac book) it doesn’t work.
Most of the time, the image is locked in a zoom-in position :way too close to be able to draw and work properly. Can I have an answer please???
PS: the problem does not exist at all on STB pro 7.