The issue was that the wrong flag was passed to
`ANIM_nla_mapping_apply_if_needed_fcurve` resulting
in the handles not moved back in this method.
This issue was only visible when pasting on top of a single keyframe,
or when the key had free handles. That is because the handles would
be recalculated otherwise.
Pull Request: https://projects.blender.org/blender/blender/pulls/140542
4fbcdba21e