I know this thread is a few months old, but I wanted to share my recent experience.
About a year ago I decided to brew my first hard cider. I did a lot of research, bought unpasteurized cider from my favorite orchard and other needed ingredients. Followed all the steps, racked 3 or 4 times over a few months to get the clearest cider possible. Everything was going great. Bottled it up, and sat on it for awhile waiting for it to carb up. Tried it after two weeks - flat. But I decided to be patient! Tried it about a month later - flat. At this point I was starting to worry, but didn't want to give up, so I let it go another month. Still flat. Apparently I messed up somewhere.
Fast forward until about a month ago. The cider was still sitting in bottles, having been put out of my mind. So I chose a bottle at random to see if, after all this time, something carbed up. And guess what. FLAT!
Or so I thought. I chose another bottle at random, and when I opened that one, it erupted out of the bottle. I opened the one next to the volcano bottle and it was the same story. The only thing I can guess is that I didn't properly mix in the priming sugar solution, so some bottles got a lot and others got none.
So considering it had been about a year, and there was no way of telling how a bottle may have turned out, I decided to re-bottle it. I did a lot of research and was fully aware of how it could totally ruin the cider, but to be honest, at that point I didn't care. I'd already waited a year, and couldn't give out a damn bottle. And I had yet to really taste my creation as it was meant to be.
Here's what I did. I sanitized my bottling equipment and bottle caps, and boiled up another batch of priming solution. I them opened up the bottles and very slowly, carefully dumped them into the bucket, along with the new solution. Some were carbed, others weren't. All went into the bucket. Then, without resanitizing the bottles, I refilled and recapped them.
I was prepared or a nasty, oxidized, potentially over-carbed result. But I was wrong. It worked like a freaking charm. The bottles are perfectly carbed, and it tastes exactly how I intended it to. In fact, I can't tell a difference in flavor from the flat cider to the newly carbed stuff. It is great.
I don't say all of this as an advocate of re-bottling to solve all issues. But rather than dump it all down the drain to recoup my bottles, I figured I would make one last ditch effort. And it paid off.
So there's my story. It works sometimes. Maybe it wouldn't as much with a true beer instead of a cider, but in this case it was a success.