Create Requisitions with Credit Lines not working on a smartform

Summary:

I am testing enabling the 26B feature Create Requisitions with Credit Lines, I can use the feature successfully if entering a requisition line, but we would like users to use a Smartform.

When I try to enter the details on the smartform I am prompted to enter either a zero or negative amount, however when I do that I receive an error.

My Smartform is set up as below:

When I enter a negative value I receive this error

If I enter the value as a positive amount I then receive this error

Has anyone else encountered this issue?