Dan this complicates things that 1) it's opened back up and looks horribly contaminated and 2) it's a friend meaning, in our business.... that you can't charge what's appropriate if you are going to have to jump through your sphincter to repair it. There is also the added problem as well it's been broken prior and however the prior repair person was satisfied with the joint as-is is what you have if you attempt to reglue. Lastly, the fix didn't work and that's telling as well.
With all that aside IME this is a chop it off and make a new headstock situation. I would not trust the prior work to clean, fit, and reglue especially if this is a potentially valuable or coveted heirloom instrument.
We likely would not take it in and the work would be sands guarantee if we did anything beneath what we would consider to be a best practice such as making a new headstock, refinishing, etc. and that would cost big.... bucks for a busy shop like ours in both opportunity costs and what we would have to charge the client. And again this is a friend..... See I really do listen...
My suggestion is to be completely honest with the client and unless you have unlimited time available to you sometimes value and quality have a cost, friend or not this should be at least shared.
Oh yeah, in all of this pedantic mess is what you really wanted, no way I would trust that existing, failed joint clean out or not it has to go or this things going to be a headless horsemen again.
In 40 years I have NEVER seen a joint that turned black. I wonder if it was contaminated glue, or someone added a color to the glue. It's WEIRD. I'd open it up and attempt a cleanup and reglue, and a finish touchup would probably be in order. The big BUT here? The job would be more expensive than normal, and NO GUARANTEE. Up to the client to risk it.
