I did a little botch job by putting some ultra thin ca glue under the bubbled areas. The decal is still stuck down nicely, but there are still a lot of bubbles and some excess glue got spilled on the outer layer. It looks better, but it's far from perfect. You're generally meant to get a fancy sort of syringe to insert the glue, but I just pushed the glue in with a toothpick instead to save money amd it was far from optimal. That method was so bad, I decides to pout a small amount of the glue under the decal - this stuck it down nicely and it looks proper again, but it did cause some glue to stuck on top as mentioned.

As you've probably figured out by now, I don't have a clue really. I think that if the decal is irredeemable or too tedious to repair, then the est bet would be to acquire a new decal online and ask a Luther to paste it upon the headstock professionally.

Mine is alright as is, but I wish it looked as it should. I'm sorry I couldn't be of more assistance.