Hello D,
You could buy some old fashioned fly paper strips. Cut it up into thinner strips then wrap them around the branch or twist tie the strips sticky face up near where the damage is occurring. If it is insect damage it will capture whatever it might be and then you can identify what it is. Then treat accordingly. If it is some type of animal it will at least grab some hairs for you to work out what it might be.
Oh a better photograph in close up would be helpful too. It was hard to work out much from the earlier snaps.
Kind Regards
Lionel

