If I open the page, and fist scroll down to Campus, the text slides in from the right.

Now, if I scroll back up, select Germany, then scroll down, the text is still there.

This tells me that the slide in from the right effect is being triggered at a certain scroll point. But, the filter is altering the page section heights, thus only when you scroll down far enough in your scenario does it trigger it slide in. Which you won’t see as it does so whilst you are blow where it arrives.

This would be very complex to resolve, unless you know what the code is that calculates the trigger point for the slide in action, and then you could run that again after our ajax runs.