There seems to be a lot of this about.
There was another thread recently about similar symptoms.
This was my post.
https://www.backyardchickens.com/threads/hen-with-suspected-neurological-damage.1282195/
Unfortunately symptoms such as you describe which are near identical to the symptoms my hen has and the hen in the post I can't find, are not going to be cured by crop checks, trimming spurs, or nutridrench and moulting won't produce such symptoms either.
It would seem that this type of behavior falls under the broad heading of wry neck as mentioned by Eggcessive in post 3.
I have tried the vitamin E and selenium treatment and it hasn't made the slightest difference. I've been to the vet and contacted two others I have found in the UK who specialize in fowl and the general consensus appears to be the problem is neurological and there is no treatment. The other possibility that gets mentioned is Mareks disease which I haven't ruled out.
Apart from these backwards walking, head weaving fits my hen seems very healthy.
If you read the above thread I started there are some worthwhile links provided by Eggsesive; it was the treatment schedule in one of these links I followed with the hen here.
I've come to the end of the line with the hen here and have accepted that while there are drugs on the market that may help, the expense and associated health risks are just not worth it for an otherwise healthy hen.