Hi Carlo,
Thank you for letting us know, this is indeed an issue, I can confirm it.
If you want to fix it before the upcoming release, you can do so by editing one of the plugin files:
1. Open up the wp-content/plugins/ajax-search-pro/backend/metaboxes/default.php file via FTP
2. Change it’s contents to this
3. Save
After the modification, the save process should work.