That is annoying.We have a great firewall here!

@Megan Clancy The answer is reasonable firewalls between sets of assets, and plenty of insurance. 

Get a new PM who will act as a true firewall and also implement your goals and strategies.

For example: there can be no plastic pipe in plumbing, the walls between units must meet certain specifics to be a firewall, if it is forced air each unit will need its own furnace as units cannot share a return air duct, etc.  

If you get a lot of these or have high net worth you might want to think about a intermediary LLC to act as another firewall.

A lot line will have to be "implied" when figuring distance between existing structure, firewalls and window % of the facade. 

Specifically looking for both the fire suppression system and if you have firewalls with the other tenants.  

To be properly repaired, the firewall (parapet) needs to be rebuilt down to the roofline so that it is plumb.

One of the main reasons for me is creating a firewall between the growing equity in each property.

Of course, you're always exposed if they prove fraud or negligence on your part, but the LLC along with adequate liability coverage presents the best firewall, I think.You might want to look up the use of a land trust with beneficial interest held by your LLC.