I serve them a 10-day Notice to Comply and document the incident in their tenant file.

Certain types of incidents (ie travel industry impacted terrorism, Mandalay Bay shooting) and really major financial crashes have a larger impact and tend to be longer lasting.

I would report this incident to the National Association of Realtors.

After I make such comments, the poster will usually come back with claims of how many attorneys have been "involved" in developing the contract, how it has been used 1,000 times without incident or has prevailed when they used it.First of all real estate compliance is a local and state issue.

Same if I get sued because of an accident or incident on one of my properties, I am protected correct?

Isn’t this a huge co-incidence that someone is making another offer tomorrow after a few hours of me accepting their counter offer?

With this incident occurring in California, new law effective July 1 : https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?

You do not want to have all your resources vulnerable to some unfortunate unexpected incident. 

Documenting all of these incidents will help your case.

I did some due diligence and in my best guess this was an isolated incident that I can rectify fairly easily.