I have an idea to fix this problem (bug) with the mutation.
Easy fix, done.
EDIT: not quite, something is overriding the price on the new order when the Ticket is Closed (Submitted)... still looking in to that.
EDIT2: got it beat, done.
I can also automate the Prompt for Price input for 0-priced Products, but it will require a specific Automation Command to be configured in SambaPOS (ie. like QMX Price Prompt ).
EDIT3: automation is in place for system properly configured with QMX Price Prompt Automation Command.