The basis here because of the "patriot Act" is to stop (theater) mainly terrorism. the banks are now
responsible for "knowing" their customers, and their banking habits.
IMO do not close the account and go elsewhere to solve this particular issue, that will only raise more red flags.
You just need to go up the ladder. Do not give them a false BOS, that is federal bank fraud. Do not withdraw $5K at a time, that is a federal offense of "structuring".
You are currently doing nothing wrong, they just need to calm down, and you need to help them with that process, as BS as it all is.
Two weeks ago I withdraw 5 figures from my local bank (of 15 years) in cash for a deal that fell apart hours later in the day.
I returned to the bank drive thru hours alter to redeposit it. The bank teller asked me where I got the money I was depositing, I pointed to a nearby teller and said "from her earlier today"