Here is the answer, our developers provided in a similar support requests from another user
We are letting RSEventsPro build the URL:
$link = rseventsproHelper::route('index.php?option=com_rseventspro&layout=show&id='.rseventsproHelper::sef($element->id, $element->name).$language);
Some extensions however need a menu item ID to build the correct SEF version of a URL. Do you have one in particular for events/calendar/location? It should be shown on the menu items listing.
If so, you could try editing the file administrator/components/com_acym/dynamics/rseventspro/RseventsproInsertion.php
and replace the line 316 by:
$link = rseventsproHelper::route('index.php?option=com_rseventspro&layout=show&id='.rseventsproHelper::sef($element->id, $element->name).$language.'&Itemid=123');
Where 123 is the id of your menu item.
If that resolves your problem, let us know so the developers can add this menu item ID parameter in the add-on configuration