Error when Slot has been taken

Good day Stephen,
Thank you for a very good Plugin!. We love it and use it to facilitate the sign up of 144 slots in our 72 hour Prayer Vigils.
PROBLEM:
when multiple people try to reserve the same slot at the same time, an error is displayed when one person reserves a slot and a second person tries to reserve the same slot. They keep trying to reserve the same slot with no luck.
SOLUTION:
When an error occurs, query the slot and when it has already been reserved, display “This Slot has been taken. CLICK HERE to exit and refresh the page.”. Make the URL in the CLICK HERE cause the browser to exit and refresh the page.

Thank you again for a great Plugin. We would be happy to donate toward this solution.