Lost Carbonation on 1.5 year old Barleywine....

So I have a Bourbon Barrel Barleywine that is nearly 1.5 years old now and I have been enjoying for the past year or so with all of the bottles being carbonated. Within the past 2 months, all of the bottles that I have opened have been completely flat...quite a disappointment being this beer has so much age on it and is only getting better and the supply is getting smaller.

The only cause I can think of is that the bottles were not sealed perfectly and over time they lost carbonation? Any other ideas on how this could have happened??

Solutions? I'd rather not pour out of the bottle and re-prime/re-pitch for fear of oxygenation. But at an ABV of ~11.5% and no Oxygen, is there any chance of it recarbonating if I simply open each 22oz bottle and add some alcohol tolerant yeast?

Any suggestions would be appreciated for the best possible method for saving what is left of this delicious brew.

get some carb tabs from the lhbs, drop 1-2 in each, and recap. that should work. should be enough carb left to repel oxygen while the old lid is off

I had the same thing happen to my Bourbon Barrel Porter. Funny thing is a Dunkle I bottled the same day is still fully carbed.... What could have cause this with the Porter?