Ok just checked, there is no track motion active. And the reason my cursor never moved is because to simplify the problem I removed the second keyframe, so now in those two pictures we have one keyframe.
I’ve done this to show that (in the first picture) the crop box and preview look the same, but just when I drag it a bit bigger (on the same keyframe) the preview box doesnt match the crop box anymore.
The same result happens in the render.