I have a Summit Bushmaster climbing treestand that is a couple of years old (it is one with the air pillow seat). The past couple of evenings, it has made a pinging or tapping sound when I shift my weight or move my feet slightly. It has NEVER done this before. While the sound is not real loud, I' m afraid it might be loud enough to alert a deer if there is one in close to me. Does anyone have any thoughts as to what may be causing this sound and how to stop it?