I just discovered what it seems to be a crack in the wood, it runs just parallel with the grain, so at first I thought it was a crack. It’s an Atkin with Aged finish, so the whole body and neck has the finish checking. Looking closely could be a deeply crack just in the finish? Deep enough to feel it under the fingers?
Hi, it's a bit hard to judge from the photo, but I would have a stab at a timber crack causing a lacquer crack. Is the lacquer thick? You could remove a tuner to see how thick it is if it's not obvious.
I have seen these cracks caused by an over-tightened truss rod.
Yep. I had a hotrod truss rod break out thru the back of the neck in that area. Repair required fretboard removal, additional wood added to the bottom of the channel and a new truss rod installed with a shallower profile. The recommendations on AGF to return it are probably the way to go.