Error in participant counts on events with waitlists

There seems to be a participant calculation error at a specific stage in the workflow for events using waitlists, which is making the waitlist feature unuseable.

When a place becomes available on an event with a waitlist, the reminder email is being sent correctly to the person at the top of the waitlist, but when this user clicks on the registration link in the email, they see the 'Oops, it looks like there are no spaces' message.

At the confirmation page stage, it looks like Civi is counting all participants as opposed to just those with counted set to true. Are you able to take a look?

Thank you, Charlie