Sorry but it wasn't a Superfly (though I did have one which was problem free).
Ashdown repaired a Giant for me, FOC.
I still rate them as one of the best companies in the UK
I have a 33" built by @Lukasz Chyla and a 30" built by @Jabba_the_gut both have a low B that I am happy with.
I have tapewounds on both so that may have some impact of the playability.
What can I get for £5k?
Shopping around I'm pretty sure that there are name builders who could custom build me as good, if not better, basses for less.
I wonder what Bernie at GB could build me for £5k...
How could you show the damage "was 100% attributable to the tech while they worked on it,"
I'd be concerned about ruining a good relationship with my luthier over something that may not have been their fault.
Experience tells me that nobody is going to own up to damaging the bass. It was never going to stay perfect forever, no matter how well cared for.
Accept the inevitable and live with the chip.
You should contact Nick Smith ( @doctor_of_the_bass) who had an endorsement with Enfield and was their chief demonstrator.
Most of the YT videos you'll see are with Nick.
Is there any BCers on the list of "BCers able to help fix.. " list nearby?
Personally I'd send somebody like@Andyjr1515 a PM to see if he could squeeze it in his busy schedule.