Completed Order email crashes with multiple recipients

When sending the Completed Order email, Event Tickets throws a fatal error if I enter more than one recipient in the “Additional Recipients” field. This worked previously and only became an issue with the latest release: 5.26.0.1 

PHP Fatal error:  Uncaught InvalidArgumentException: Email address is invalid.
in /wp-content/plugins/event-tickets/common/vendor/vendor-prefixed/stellarwp/shepherd/src/Tasks/Email.php:81
Stack trace:
#0 ... Shepherd\Tasks\Email->validate_args()
#1 ... Shepherd\Tasks\Email->__construct('paul@xxxxxxxxxxxxx.com, other@xxxxxxxxxxx.com', '[xxxxxxx]: Completed Order', ...)
#2 ... TEC\Tickets\Emails\Dispatcher->send()
#3 ... Completed_Order->send()
...
//actual emails removed for privacy

Steps to reproduce:

1. Go to Events → Settings → Emails → Completed Order.
2. Enter two or more emails in “Additional Recipients”, separated by commas (as the UI instructs).
3. Complete a test order.

Observed behavior:

• With a single recipient, the email sends fine.
• With multiple recipients (comma-separated), checkout crashes with the error above.
• The system is treating the whole comma-separated string as one invalid email instead of splitting it.

Expected behavior:

• Multiple recipients should be parsed correctly when separated by commas, as the settings field indicates.

Workaround tested:

• Creating a single distribution list/alias and entering only that email avoids the crash, but the “multiple comma-separated addresses” feature appears broken in this version.

Can you confirm if this is a known bug, and if there’s a fix or patch in a newer release?