Nigel: thanks again for reporting this. It’s been recorded as a bug and may not be an issue in the next version (due to the significant changes being made) but if it is then it ought to be addressed.
In the meantime, if you feel confident making a few changes, please locate this file:
wp-content/plugins/events-calendar-pro/resources/events-admin.js
Make a copy in case you need to restore it for any reason, then replace the existing contents with this code. That should solve the problem.