After careful assessment of export related changes in v9, I’ve resolved the current broken link issue (I think!) by exporting the aTbRef9 TBX using v8.9.2.
So, links should work, and any broken ones need fixing at source rather than being broken by v9.0.0 export. Also, if you spot pages where the links are clearly not correctly aligns with the correct anchor text, I need to know as that definitely needs a manual fixing in the TBX).
Site is at A Tinderbox Reference File
I’m going to hold off on updating all the re-directs etc, until v9 is patched an exporting correctly. But, tentatively, aTbRef 9 is now working.