Carefully consider how your boat is aligned within the slip with respect to neighboring boats. In the picture above, both boats did not have fenders to provide any separation. The mast on both boats were perfectly aligned fore and aft in the slip. And the mast height on the red boat easily slipped inside the shroud triangle at the top of the mast on the green boat.
Warning signs: If you are noticing damage to your windvane at the top of the mast, consider if heavy wave action is rocking the boat and the mast is swinging far enough to contact your neighboring boat.
How to Check? Stand on your boat at the shrouds and start rocking the boat side to side. Look up and observe the arc of the mast tip swinging near the other boat. If it appears it may contact in heavy wave action when the other boat is also rocking in the same motion, then consider re-adjusting how your boat is aligned in the slip using your dock lines and strategically placed fenders. Adjusting your boat so it is angled in the slip can help immensely. Adjusting the boat fore and aft in the slip so that at least 3 feet of offset between the masts on either boat is also beneficial.