As I understand it, the relief is okay around the 12th fret BUT, and I am no whizz with this stuff(why I trusted the original builder initially and then again to fix it!)...beyond the 14th fret etc, there are weird issues, maybe a twist?
The truss rod is maxed out, so....as I understand it, there are ways around this....spacer/washer etc.
The frets were levelled, well....attempted, could not be done completely....top end of the neck has something going on either separately or in conjunction with the truss rod being maxed out when that was attempted.
Plan is to let it sit through the seasonal change and then eyeball it IF it remains 'unstable'.
After that, I will need to take it to Sims and go from there...