Checkout random characters with credit card payment method

-- HikaShop version -- : 5.0.2
-- Joomla version -- : 3
-- PHP version -- : latest
-- Browser(s) name and version -- : all

When a customer pays on our site using the CREDIT CARD payment method,
Instead of the normal t"order confirmation" page, this mess of characters appears.

The checkout issue ONLY happens with the credit card payment method.

I have emailed hikashop support for over 2 months continuously without getting any resolution or assistance on THIS matter.

Normally hikashop is the best ever!
I need help please.

Hi,

You said yourself in a previous email that this issue is linked to someone customizing the invoice:

This problem happened after we were having someone try to make our bookshop invoice display better

So from what I understand, you hired someone else to customize the invoice, this linked to the invoice generation messing the payment process.
Now, I'm sorry but I didn't had the much time in the past few months. I was busy with normal support and working on our extensions to support Joomla 5. And your issue falls outside normal support.
That's something you should have the person who made that incorrect customization fix for you.

Nevertheless, the Christmas period is coming around and I should have more time during that period to look into it.
So, please send an email and provide all the necessary information in that email for me to look into it:
- precise instructions on how to reproduce the problem
- a backend access
- a FTP access

thank you!!!