The primary recipient refunds the fixed payment from their PayPal account; what's happening?

I am developing a PayPal application where

• Primary receiver = service provider receives 90% of the payment.
• Secondary receiver = market, receives 10% payment.

This all works in a Sandbox environment, but there is a catch - when the primary recipient logs into their PayPal account and manually returns the payment received, the secondary recipient does not automatically return their 10%.

etc .:

• The primary recipient was paid $ 100, automatically received $ 10 by the secondary receiver.
• The primary receiver decides to return using PayPal the account interface.
• $ 100 refund; but the secondary receiver keeps his $ 10. The primary receiver is now out of pocket for $ 10.

I would like the secondary receiver to automatically refund their portion of the payment if the primary receiver issues a refund.

From reading the documentation from the Refund API ( https://developer.paypal.com/docs/classic/api/adaptive-payments/Refund_API_Operation/ ), I thought this was the default behavior, regardless of whether the refund was initiated via a call API or manually through the PayPal account interface.

Am I getting this wrong, or is it just a bug with the Sandbox environment?

It would be helpful if this cleared up as it could not find existing threads in this question.

Update

PayPal tech support told me the following:

Thank you for contacting Merchant Technical Services. From my understanding that you would like to have, when the primary receiver makes a refund, the secondary receiver will automatically issue a refund. If you want the entire recipient to return the amount, you need to transfer the key. May I know how the payment was made? If it uses the Pay API operation, you need to use the return API to return the transaction. Refunds are not possible using a PayPal account.