Contribution/membership receipt - unable to disable

I did have a look around already but thus far without much luck.

We recently turned off the ‘Email Receipt to Contributor?’ option on a membership join page. I did check the ContributionPage settings and they show that the ‘is_email_receipt’ is off:

"values": [
    {
        "id": "5",
        "title": "Join xxx",
        "is_email_receipt": "0"

However new members joining are added as

 "contact_id": "14971",
    "currency": "EUR",
    "contribution_recur_id": "4696",
    "receive_date": "2020-07-06 00:51:41",
    "contribution_source": "Join xxx"

  "id": "4696",
        "contact_id": "14971",
        "amount": "10.00",
        "currency": "EUR",
        "frequency_unit": "year",
        "frequency_interval": "1",
        "start_date": "2020-07-06 00:51:38",
        "is_email_receipt": "1",**
        "contribution_type_id": "2",

Now I appreciate that for contacts that joined before switching off the receipts I would have to update the ‘civicrm_contribution_recur’ table to stop those but I cannot find a reason why new contacts are still being added with the "is_email_receipt": "1"

We use Stripe as the payment processor and the ‘Allow Stripe to send a receipt for one-off payments?’ for settings is disabled.

We are also using the nz.co.fuzion.transactional extension so I can see the receipt that goes out on the contact record (the Civi one).

Can anyone shed some light for me?

Civi 5.24.4/Drupal 7

Thank you!

    'is_email_receipt' => !empty($params['is_email_receipt']) ? 1 : 0,