Usability:
After verifying an invalid address the info/error text apears in green. It should be red to indicate that there is something wrong, to me some seconds to trigger on the green ("all is right"-looking text)

The droppdown menu/input field for the seller address acts 'weird'. After copying (ctr-v) an address in it sometimes opens up and default selects the old (default) value which gets promptly selected and overrides the wanted (copied) address.