Hi Federico,
It definitely looks like it is. Can you please try a modification to see if this resolves it:
– Open up the wp-content/plugins/ajax-search-pro/includes/classes/Index/Tokenizer.php file on your server, replace it’s contents with this
– Then wp-content/plugins/ajax-search-pro/includes/classes/Utils/Str.php file, replace with this
– Save them both, and try to replicate the bug, it should no longer appear.
Please let me know if this helps.