Get connected "from" instead of "to"?

I have a post type called customer, and another called case-study. Each customer can have multiple case studies connected to it. The connection type is case-study_to_customer. I’m trying to get a list of customers, with their connected case studies.

I’m using WP_Query to get the customers, and then I am using WP_Query to get the case studies, passing the following parameters in the array:

‘connected_type’=>’case-study_to_customer’,
‘connected_items’=>$customer_query_object

This second query fails with an error: “Could not find direction(s).”

Does p2p support retrieving related records like this? If not, what is a better way of doing it?

https://www.ads-software.com/extend/plugins/posts-to-posts/