I have found a number of other users posted this question in the forum over the years but I cannot find a resolution anywhere.The way the Rental Property Calculator derives the "Profit if sold" number seems to have an error in it if you are using the function to increase the rental rate and expenses each year.

I would find attorney if your PM did not give you any resolution. 

I really doubt many would dispute that claim here.

That creates a civil dispute that police may or may not assist with until you go to court over it. 

Any resolution to share the costs would need to acknowledge the restricted nature of the common elements involved, such as the windows."

I have also been involved in litigation on subordination agreements where they are disputed.

I would contact the collection agency and ask for courtesy delete and, if that doesn't work, dispute it. 

Rented the house 2 years, had a dispute with one neighbor and is now moving out.

This is another reason why having binding arbitration in all your contracts...it can be far less expensive and much faster to remedy a contractual dispute. 

Discussing a fair resolution with the renters could mitigate any potential legal ramifications while maintaining a positive landlord-tenant relationship.