meta http refresh being blocked

I'm wanting to redirect from the form to a payment page using the thank you message.

The code i'm using is:

<meta http-equiv="refresh" content="6;url=https://www.payway.com.au/MakePayment?biller_code=1111&merchant_id=1111&payment_reference=Dinner&payment_reference_text=Programme&payment_amount={total}&payment_reference_text_help=" />

This works on all the other forms I have but now when I save the form the meta tag is being changed to m-eta.

Can anyone tell me what might be doing this?

Thanks, Chris A

I found the answer. It's RSFirewall. I had to add an exception with these parameters:
Exception Type: component
Use RegEx: no
Match: com_chronoforms5
Skip PHP protections: no
Skip SQL protections: no
Skip JS protections: YES
Skip Upload protections: no
Reason: Allow <meta> in content
Published: Yes