Add Cloneable Group using update_post_meta() whilst preserving existing data

Hey,

When I try to add data to a cloneable group which already has a group the data overwrites the existing group. How do I add a new set of data whilst preserving the existing data?

Group code

                'name'            => __( 'Payments', 'your-text-domain' ),
                'id'              => $prefix . 'fr_payments',
                'type'            => 'group',
                'clone'           => true,
                'hide_from_front' => true,
                'fields'          => [
                    [
                        'name'     => __( 'Amount', 'your-text-domain' ),
                        'id'       => $prefix . 'fr_payment_amount',
                        'type'     => 'number',
                        'readonly' => true,
                        'prepend'  => '£',
                    ],
                    [
                        'name'     => __( 'Stripe Payment Intent ID', 'your-text-domain' ),
                        'id'       => $prefix . 'fr_stripe_payment_intent_id',
                        'type'     => 'text',
                        'readonly' => true,
                    ],
                    [
                        'name'     => __( 'Date Paid', 'your-text-domain' ),
                        'id'       => $prefix . 'fr_date_paid',
                        'type'     => 'text',
                        'readonly' => true,
                    ],
                ],

Update code:

    $payment_meta[] =  
    [
      'fr_payment_amount' => $this->stripe_pi_amt,
      'fr_stripe_payment_intent_id' => $this->stripe_pi_id,
      'fr_date_paid' => date('j F Y')
    ];

    update_post_meta($this->order_id, 'fr_payments', $payment_meta);

Thanks