When offering a waitlist with PayPayExpress, "Continue" button disappers

[SarahG (FountainTribe)]

I have a paid event set up with PayPalExpress, which offers a waitlist and online registration.

When someone attempts to register online (The event has lots of room), the "continue" button at the bottom of the screen is missing.  If I remove the waitlist config, then it works as expected.   This is happening in the public sandbox at:

http://d45.demo.civicrm.org/civicrm/event/register?id=11&reset=1

Any ideas on this?