Sunrace Sturmey Archer have come to the party and sent me a new internal mechanism to fit to the existing hub shell
I did check the design of the sun gear pawls - and they have been changed to have only one tooth.
Hopefully better luck this time. I'll post a progress report in a couple of weeks when I pull the hub apart for an inspection.
On a side note I wonder if they have QA issues as the final drive pawls were binding in their housing. I had to swap this part out from the original hub