Images in Slider don't render size properly


I’m new to Webflow and I’m trying to make a slider with Lightbox inside of it. I managed to make it look and behave as I wanted, but when I go between slides, the images first fill the whole slide and after a second they resize to the correct view.
If I set the mask’s Overflow to visible everything works fine.
(See gif below for reference)

Is there a way to fix this?
(I’m using the free plan so I can’t add custom code :pensive: )



This is the structure:

Is there anybody who could help? :grin: