Rude, disrespectful, immature owner

I'm on the Board in my HOA.
Contacting info is: Mail, email or voicemail
This tells the members that an immediate response is unlikely.

Responses can be as simple as - Thank you for the information the board will take it under consideration at our next meeting

If the issue is not an HOA matter, tell them that and who they should contact (police, animal control, etc.).

If the issue is a neighbor v. neighbor issue, tell them the Association does not get involved in neighbor v neighbor issues (my last association actually had a policy stating this. 2 or more lots would have to complain for the HOA to become involved).

If they knock on your door, politely tell them that you are not available for HOA business at this time and to please send an email. If it gets real bad, get a camera and simply don't answer the door.

If in person, always respond, I am but one vote on the Board and things are done by majority vote. Please place your concern in writing so nothing is missed and the Board can respond to it at our next meeting.

What is this person complaining about?

Not necessarily. The OP said the attorney assisted the board with the previous skirmish, but didn't say if this landed in court and a judge ruled in the association's favor, but only awarded attorneys fees. This happened 10 years ago, so its too late to refund any money anyway. The OP didn't mention the documents, so we don't know if that was an issue

Unfortunately, there are timesin HOA land land where some people are a complete pain in the ass and the only way to address them is to be as professional as possible without resorting to yelling, cussing fistfights, etc. Tim's suggestions are the best - establish a email account for all board members and then decide what to do. If it's a simple maintenance issue, that can go to the property manager. If it's something that's related to an upcoming agenda item, let the homeowner know and encourage him/her/them to attend and listen to the proceedings.

Actually, the board should have something on its website or newsletter reming everyone of what's expected when it comes to contacting the board and overall processes when it comes to requests or complaints. Board members have lives outside the association and shouldn't have to deal with calls or unannounced visitors all day and night. You should expect an acknowledgement that your letter or phone message has been received, but that doesn't mean you'll get it as soon as you hit send or hang up. What you think is an emergency may n I t be the case, especially if it doesn't involve an immediate danger to life ir property. And if you and your neighbor have issues, you should be adult enough to resolve it ir perhaps get a friend or two to meditate. Or go to court and let's see who wins.

I think we have the same owners twin living at our association.
What we have done is add the following to our rules and regulations
General Conduct

Board members and residents shall not engage in any abusive or harassing
behavior, either verbal, written or physical, or any form of intimidation or aggression directed at other members, residents, guests, or vendors.
We then added the following to our fine schedule.
Abusive or Harassing behavior- either verbal, written or physical, or any form of intimidation or aggression directed at other members, residents, guests, or vendors.
First Violation- a fine of $100.00 and any expenses incurred and or actual damages
Second Violation a fine of $200.00 and any expenses incurred and or actual damages
Third and subsequent violations $400.00 and any expenses incurred and or actual damages

Since doing this we have not had any issues with said owner. We also advise any vendor doing work at that residence to leave immediately if owner becomes abusive or disruptive. If needed we tell them to call the police.

We have not had an issue for over 2 years now. Life is good

Karen T, we took the same step and added a harassment behavior rule into our Rules and Regulations. We took the Minnesota State statute and incorporated it into the Rules and Regulations.