CiviEvent shopping cart - price set defaults lost, 2nd participant price replaces 1st, 2 email addresses

Using WP (which I think doesn't affect this code) - add event to shopping cart, then checkout - I ask for email and name in the event template, but a 2nd email address is asked for in the 'Cart' checkout. Price set defaults are lost (no default values selected). If I select price 1 for participant 1, add participant 2, and select price 2, the total charge will be price 2 x 2, not price 1 plus price 2.
See attached screenshots from CiviCRM Demo