Between the finish and the wood something must have moved relative to the other to cause a crack. That is for sure. But when I take the neck off there's no visible cracking or separation on the inside of the neck pocket on mine.I always consider these are in the wood. Finish doesn't just crack without having the wood move under it. But on anything basswood and especially plate joint as said, it's not a question of if but when.
I've see them repaired by Hoshino, you can always tell. Leave it alone.
That sucks :sad2:My JS1CR developed it recently too. I am guessing for me it was the temperature changes in the east coast even with heating and trying to maintain the house at a constant temp. My guitar has not been moved from my room. I restrung the JS1CR and noticed it. I am sure it was not like that when I got it around April because I inspected that area as I had a JEM with that issue once.