Popping up/reloading images when going to the next layer

Hi everyone,

I have a bit of a special problem:
I have created a quite complex software simulation with tons of triggers, screenshots and different actions to simulate our companys ERP-system as closely as possible.

The whole simulation is based on about 20 layers with the users going through them in linear order. Most layers contain forms, where users enter data via textbox or chose an option from a simulated dropdown-panel, then hit enter or click the respective option and thus go to the next layer.
The next layer then shows an updated screenshot with the data correctly entered, the user goes to the next field of the form and does the same thing again.

Now the problem is when transitioning from one layer to the next, the foremost screenshot (the one with the updated data) always fades in (very quickly) instead of being there from the getgo.
I've of course checked the timeline and animations, but everything is set up correctly. There's no entering-animation selcted and the screenshot is anchored to the start of the layers timeline. I've tried tons of different things but i just can't get rid of this and it really bothers me, because it doesn't look clean and you can always see what's below the foremost screenshot when going to the next layer.

Interestingly enough when there are two screenshots placed on top of each other on a layer, the second one is showing from the start, it's only the foremost one that pops in, although all their settings are exactly the same (I double-checked everything).

Does anyone have an idea what could be causing this?

Unfortunately I am unable to share the story file publicly because it contains data from our ERP-system.