Thanks for confirming.
The GTM code I’m getting is from a 3rd party, I have no control over it.
It’s coming from the IT department who manages the Transport and Main Roads department in my state.
I think all I can do now is flag it and ask them to get some better GTM code.
Basically I got sent a notepad file via an email attachment containing the code.
I think the issue now has been properly isolated. Feeling more confident about it now.