C++: Program crashes when I try to access a private class string variable. Why is this, and what can I do to fix it?

I am writing a bank account program that provides a menu system for the user, which allows them to choose between 4 options: A) Add a customer, B) Print all customer data, C) Update customer data, and D) Exit program. Each option performs separate tasks. The option I am focused on for this question is Option A.

Option A is supposed to generate a new bank account object and ask the user to input the account holder name, the initial deposit for the account (how much money to start with for the new account), and the interest rate. It then needs to set these values to the correct private values in the bankAccount class for any given object.

Code for main.cpp before Option B (there is a little more code after this, hence the lack of backward brackets at the end, but I want to try and keep this more concise):

#include <iostream>
#include <string>
#include <cstdlib>
#include "header.h"
#include "implementation.cpp"

using namespace std;

int main()
{
    //array of bankAccount class objects (up to 20)
    bankAccount account[20];
    string menuInput = "";           //used for menu loop input
    string accNameInput = "";        //used for account customer name user input
    float depositInput = 0;   //used for initial deposit input
    float interestInput = 0;  //used for initial interest input
   // int customerCount = 0;    //used to compare to static int to determine # of customers in memory

    int static i = 0;

    //while loop keeps user in the menu until they choose to exit program

    while (true)
    {

    cout << endl << "Enter a letter option below: "
        << endl << endl << "A: Add a customer" << endl << "B: Print all customer data available"
        << endl << "C: Update customer data" << endl << "D: End program" << endl << endl;

    cin >> menuInput;

 //Option A: Add a customer
 if (menuInput == "A" || menuInput == "a")
 {
     //checking for max customer limit
    if (i > 19)
    {
        cout << endl << "Cannot add customer; Max customer capacity reached." << endl;
    }
    else //
     {
        ///Creates a new customer account and asks for new customer name,
        ///initial deposit amount, & interest
       cout << endl << "Bank account #" << (i + 1) << " created." << endl;
       bankAccount account[i];     //new bank account object created

        //time to set the name for our new customer...
       cout << endl << "Enter customer name for account #" << (i + 1) << ": " << endl;
       cin >> accNameInput;


       //setting initial deposit amount
       cout << endl << "Enter initial deposit amount for account #" << (i + 1) << ": " << endl;
       cin >> depositInput;


       //setting initial interest rate
       cout << endl << "Enter interest rate (without % sign): " << endl;
       cin >> interestInput;


 account[i].setInterestRate(interestInput);
 account[i].setBalance(depositInput);
 account[i].setAccountHolderName(accNameInput);


        //increments the account number counter
        i++;
     }
 }

The problem persists with setAccountHolderName() found on the last line here:

account[i].setInterestRate(interestInput);
account[i].setBalance(depositInput);
account[i].setAccountHolderName(accNameInput);

When I call the class functions setInterestRate and setBalance to set the input values to their respective private class variables, the program proceeds like normal and takes the user back to the main menu as it should. But calling setAccountHolderName crashes the program and returns this value: -1073741819 (0xC0000005).

I'll include some code from the header and implementation files below to show how I have accountHolderName code programmed in:

header.h (includes accountHolderName get/set functions):

///Name of file: header.h
#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED
#include <iostream>
#include <string>

using namespace std;

class bankAccount
{
    //private data values
    string accountHolderName;
    int accountNumber;
    //static int accCounter;  //keeps track of account numbers
    float balance;
    float interestRate;

public:

    //Default constructor
    bankAccount();

    ///Getters/setters for all private member variables
    //accountNumber
    int getAccountNumber();
    void setAccountNumber(int accNum);

    //accountHolderName
    string getAccountHolderName();
    void setAccountHolderName(string accName);

implementation.cpp (includes accountHolderName implementation):

///Name of file: implementation.cpp
#include <iostream>
#include <string>
#include "header.h"

using namespace std;

//static int definition (guess you have to define static members here?)
//int bankAccount::accCounter;

//Default constructor
bankAccount::bankAccount()
{
    accountHolderName = "";
    accountNumber = 0;
   // accCounter = 0;
    balance = 0;
    interestRate = 0;
}

    ///Getters/setters for all private member variables
    //accountNumber
int bankAccount::getAccountNumber()
{
    return accountNumber;
}
void bankAccount::setAccountNumber(int accNum)
{
    accountNumber = accNum;
}

    //accountHolderName
string bankAccount::getAccountHolderName()
{
    return accountHolderName;
}
void bankAccount::setAccountHolderName(string accName)
{
    accountHolderName = accName;
}

It seems like messing with the code in certain ways (such as completely deleting the code that comes after Option A's code, commenting out accountHolderName = ""; in the default constructor, etc.) will temporarily allow account[i].setAccountHolderName(accNameInput); to function without crashing the program, but this is incredibly inconsistent and confuses me even more. I'm not sure if the issue has to do with memory or what. I have also tried using cout to see if the input variable accNameInput from main.cpp is getting stored to, which it is.

Sorry if this is simply too much code or explaining; this is my first post and I just wanted to provide a good chunk of my code so you could see the full scale of things. All I am trying to do here is access the bankAccount class private string variable, accountHolderName, and store user input into each new object.

I tried troubleshooting this issue online but couldn't seem to find anything that had a similar issue. I'm not sure what I'm missing; any help or guidance would be incredibly appreciated.

Technically, this line:

bankAccount account[i];     //new bank account object created

Isn't allowed in C++, but some compilers (g++) allow it as an extension since they do formally support variable stack arrays with the C compiler.

Further, that declaration overrides the variable of the same name declared at a higher scope

But then you get to these lines:

account[i].setInterestRate(interestInput);
account[i].setBalance(depositInput);
account[i].setAccountHolderName(accNameInput);

But valid indices of an array range for 0..i-1 So you're already in undefined behavior with your array index out of bounds.

I suspect you really meant this:

bankAccount newAccount;     //new bank account object created

...

newAccount.setInterestRate(interestInput);
newAccount.setBalance(depositInput);
newAccount.setAccountHolderName(accNameInput);

account[i] = newAccount;
i++;