It’s time to move out of the parent’s basement, to cut the umbilical cord, to leave the nest. When you’ve got parent layers driving the position, scale or rotation of a child layer, it can be somewhat problematic to get the same motion once the layer is unparented. This is especially true if the parent layer’s rotation is animated. Ideally, just leave the layer parented. Try “baking” the parent transform into the unparented layer.
Baking essentially converts the animation into keys and removes the parenting at the same time. You can choose individual transform properties (not including opacity) or just select the layer to process all of them. The script will still process a layer even if it is not parented. In which case, it is simply placing keyframes at all frames. Orientation for 3D layers gets baked into euler rotations.