It's only a guess, but it looks as if there's a large darkish patch. I think, if curly figure darkened or stained fairly uniformly, you may not have prepped the wood to the same leveled uniform grit as parts of the stock that you're satisfied with. I think the hot reflective light spot helps illustrate some prep uneveness that might feel different to the touch, maybe soft backed sanding or some reluctance to go after it? Again, only guessing, good luck with it.