As soon as I import animations and retarget them to a skeleton, all animation data (keyframes) of the animation is removed and is no longer animating anything. Here is What I do:
I have a Side project to test in all sort of animations (currently a UE4 Project). Once I tested a animation I copy the .uasset file to the actual project (file structure is the same) and retarget the animation. This works fine in all UE4 Projects but UE5 removes all keyframes from this file.