If you search hard enough, I think you'll find where another Sabre owner replaced the entire bulkhead on one side, due to the same kind of problem. At least I think it was a Sabre owner. Could've been a Pearson owner. It was the same scheme, anyway.
I'm no boat construction guru, but ISTM those bulkheads, being primarily what holds those top shroud chainplates in place, really ought to be of one piece. But she's your boat...
cnc33voodoo makes a good point. This is damage typical of leaky chainplates. While a wet core in the vicinity of those chainplates is undesirable, it might not be a show-stopper, since, if you notice, all of those chainplates' anchoring is via those bulkheads.
82sabre might wish to have a survey done, anyway, to access the condition of the boat before putting a lot of money into her. Find a surveyor that relies not only on a moisture meter (they have been known to get it wrong), but that also does soundings.
We almost bought a Sabre 28, but the owners had painted those bulkheads, chainplates and all, to *ahem* lighten-up the cabin.