Some of the tricks that I have tried on shy gobblers is to get close and only cluck and purr softly. throw the yelps away. I also add some leaf scratching in with the soft calling. Try putting yourself between your decoy and the gobbler only if it is safe in your area to do so.
What I cant understand is them being on the limb at that time of day. Do you have a lot of yotes in the area? Ground predators would cause them to fly up at times. Fog or rain will keep them on the limb longer in the morning. Sudden hunting pressure might do it till they decided to leave the area.
Hope this helps.