The Paypal Pending Transaction Resolver(PTR) failure that @AndyRussG responded to over the weekend might have been a timing-related error. The PTR appears to have attempted to create a new recurring subscription shortly after one was set up.
The failure happened in the same method that broke earlier this week T332396: Paypal EC Pending Transaction Resolver failed (missing 'date' param)
I can see in the /srv/archive/civi1001/process-control/20230319/recurring_queue_consume-20230319-120001.log.civi1001.bz2 that the recurring queue consumer processed a 'subscr_signup' message for the related ct_id 174400055 at 2023-03-19 12:00:26 UTC, followed by a 'subscr_payment' at 2023-03-19 12:00:32 UTC.
Those events happened right before the Paypal PTR processed the affected pending record and attempted to create a new(possibly duplicate) recurring subscription for the same donor. I can see this in /srv/archive/civi1001/process-control/20230319/paypal_pending_resolver-20230319-120001.log.civi1001.bz2
2023-03-19 12:00:31,134 ERROR WD php: TypeError: Return value of [error] 2023-03-19 12:00:31,134 INFO TypeError: Return value of Civi\Api4\Action\PendingTransaction\Resolve::startRecurringPaymentAndReturnStatus() must be of the type string, null returned in Civi\Api4\Action\PendingTransaction\Resolve->startRecurringPaymentAndReturnStatus() (line 655 of /srv/org.wikimedia.civicrm/drupal/sites/default/civicrm/extensions/wmf-civicrm/Civi/Api4/Action/PendingTransaction/Resolve.php). 2023-03-19 12:00:31,134 ERROR Civi\Api4\Action\PendingTransaction\Resolve::startRecurringPaymentAndReturnStatus() 2023-03-19 12:00:31,135 ERROR must be of the type string, null returned in 2023-03-19 12:00:31,135 ERROR Civi\Api4\Action\PendingTransaction\Resolve->startRecurringPaymentAndReturnStatus() 2023-03-19 12:00:31,135 ERROR (line 655 of 2023-03-19 12:00:31,135 ERROR /srv/org.wikimedia.civicrm/drupal/sites/default/civicrm/extensions/wmf-civicrm/Civi/Api4/Action/PendingTransaction/Resolve.php). 2023-03-19 12:00:31,135 ERROR Drush command terminated abnormally due to an unrecoverable error. [error]
Also, there is something else odd that I noticed. The pending message doesn't have an email address(which I think is ok for Paypal pending messages), but the problem is that the method attempting to create a new recurring subscription expects an email address. Checkout PendingTransaction::startRecurringPaymentAndReturnStatus() and the internally called SmashPig\PaymentProviders\PayPal\Api::createRecurringPaymentsProfile()