Undefined Index: Firstname & Lastname + Cannot Modify Header Information?

Hi, I'm hoping someone can help please or shed light as to where the issue is originating from?

My site is running on version 2.3.0.2 and the issue occurs randomly (not every time) during the final checkout step, once the user clicks the final 'pay' button. I've attached a screenshot of it happening on my phone.

The payment gateway being used is Worldpay although from the error message I dont think it's related?

Having looked through the forum I did not find a similar issue, so posting it here hoping someone can help please

My site is running on version 2.3.0.2 and the issue occurs

Although, you are posting in the v3.x releases section of the forum. The issue is caused by an installed extension. The original code does not need to have any issues by sending the firstname and lastname into the order model.