I may just be that a weary buck might not like feeders. Bucks are elusive creatures and may just steer away from an obvious human presence especially if they have a good food source already. Have you tried minerals to draw bucks. I'd suggest starting a mineral lick in heavy cover and see if you can't get buck on that site. If your feeder is out in the open that might also be why. Bucks like thick cover with good exits.

Good luck