[Zfurlong]

you likely have the barrel/bucking misaligned. another potential issue is the nub itself, it could be catching on one of the side walls of the barrel upon applying hop. have you done the Teflon tape/floss mod to your barrel group? is your bucking sitting properly on the barrel inside the hop chamber? are the lips on the hop rubber torn? these are all potential areas that would cause you that issue.