Vacation Rental with Shared Maintenance Agreement

My husband and I own a vacation property in North Carolina that we rent out part of the year. We have a shared maintenance agreement with two other property owners in the cove. This agreement says that costs for maintnance and upkeep are to be shared among the three owners, this includes, the three slip boathouse, the decking around the boathouse, the deck walks to the boat house, fresh water and electricity available to each boat slip for ligthing and boatlifts. Over the past three years my husband I have paid for installation of a swim ladder, bumper guards on the dock and cletes for tieing boats and all of the utilites to the boathouse, water and electricity. We have been collecting mooring fees from our guests to offset maintenance on the dock and have paid for all of the improvements from these fees.
One of the owners in the cove is a year round resident, the other a weekend retreat and ours is a vacation rental that we will use during periods that we block or do not have tenants.
The problem is, the new owner of one of the properties decided to install a kayak launch device that attaches to the dock. It is quite nice and is a nice improvement to the property. I like the improvement, but they failed to reach out to us about installing the lift to the only area of the dock that provides a tie off for visitors or guests and it takes up approximately 18' of the the 40' dock. This measurement is an estimate of the actual lenght of a kayak 16' plus leeway, if it is resting on the platform.
I told the neighbor that I like the idea, but I don't like the location, I wished they would have consulted with me before removing the bumper guards and attaching it to the only tie off area on the dock. I will also add, there is an area behind the sheds on the boathouse that is approximately 50' that the lauch device could have been installed. If they had installed it there, I would never complain because the most conevenient tieoff space would not be impeded.
I can continue with justifiable reasons why they should move the kayak launch but I am going to stop here.
What do you think the best approach would be to keep peace in the cove and not imepede on my use of the only available tieoff area on the shared dock and be a friendly neighbor?

So basically, it is conversion of a common area for a solely private use without authorization?

Yes to all comments. There is no mention of how the common areas defined in the maintenance agreement are to be shared or used. I have attached pictures of the cove to show more clearly why we have an issue with where the neighbor installed the kayak lift. The pictures show there is ample room behind the boat house. The neighbor claims they have the right to exclusive privilages to the end of the dock where they put the lift. They have attached a "No Trespassing" sign on the lift.

You appear to want an idealized solution (don't we all?). In HOA land (or any covenant dispute) sometimes no good solutions, that give a person everything she or he wants, exist.

I would start with a polite letter asking for xyz, and asking for a response within two weeks. Meanwhile I would start looking for an attorney. The latter may not be an easy feat. Expect to spend a few thousand dollars for a legal opinion from the attorney. Seek wisdom from the attorney. E.g. is the cost of fighting this going to be worth it? What are the chances of not prevailing? Weigh all this against doing nothing.