... And you can't just "shorten the string" due to how the IO voltages are generated and split between the chips. Well, you can, but not without major surgery.

Easiest repair is Bitmain, unfortunately. Or sell them to someone willing to fiddle. I wouldn't be willing to risk not being able to fix a board with no spares on-hand, otherwise I would offer to have a look. If anyone would like to donate some definitely dead boards, however...

Cheers,

Allan.