Can anyone please enlighten me where I can find this exception logged?
main.CRITICAL: Block order_create_billing_form throws exception and cannot be rendered.  
The context is a custom payment gateway, which works 100% in front.
But, when I try and use it from admin, placing order via admin, I get the noted error logged in system.log, and that is about it.
So, I am told there is an exception, but not what it is....
Any pointers appreciated.