I have a natural ash strat which the previous owner had attempted to sand out a tiny ding resulting in a small section of bare wood showing through. I touched it up with some polyurethane gloss clear coat that I've used a thousand times before, only this time its turned yellow ? I'm not sure if the poly has turned yellow over the sealer or the wood (I'm not 100% sure he sanded through the sealer). Without removing the neck and preparing a fresh piece of wood and applying a dab of the poly I doubt I will find out. Anyone else had this ?

I've sprayed several bodies with this poly and its always dried and remained clear over several types of sealer.