OC 3.0.3.0b - Admin page - Total + Sub-Total strange

I am refresh installing OC 3.0.3.0b on XAMPP (opencart-master.zip - new download 27/2/2018 at GitHub). Test myself in admin page, add new an order (buy iMac product), after I am click the Save button, then I am click the Apply button of Payment Method, Total + Sub-Total become 0. This is my screen testing.



Or full screen image: http://abload.de/img/shipping4io22.gif

Please fix.
Thanks.

Screenshots feedback: I like those animated demonstrations. They are clear and precise.

Use the developers kit by hitting the F12 function key on your keyboard and to go the console tab. Hit the apply button again from the coupon row as you demonstrated and see if there are errors showing on the console tab.

Thank for reply.

I want to clarify further, after saving the order, I edit the order, I do not see Flat Shipping Rate ($5) and therefore the total is still $100, which should be $105.