Hi! Do you have any modifiers on the mesh you bake to? If so, check the modified UVs to ensure they are not affected by a modifier (bevel). Either duplicate a part that is affected apply all modifier, there might also be an option in the UV editor to preview modified UVs.
Thanks to your reply; it was the bevel modifier. After removing and adding some bevels, nasty lines disappeared. Guess I have to be more carefull with them. Thanks to your suggestions, it helped!