Animation on Scroll triggering a class is not working properly and consistently

[mark88008]

i have the issue, that the animation is not always working.
It's a on scroll animation which zooms in the selector which has a specific class.
Often its not working after scrolling the first time down the page, and after few times scrolling up and down, its working.

Or it's also not working after scrolling up and down, and always if I open the inspector on Firefox Dev Edition all animations are working. Has anybody a solution for me?

The Website is: gabrielschandl.com

Affected is for instance the Section with the heading "Referenzen", you can see below.

Any other selector containing the same class have the same issue.

[mark88008]

Is there any estimation when I can get a feedback on it?