diff --git a/CRM/Mailing/BAO/MailingJob.php b/CRM/Mailing/BAO/MailingJob.php
index c52b84721480..0857c950ef27 100644
--- a/CRM/Mailing/BAO/MailingJob.php
+++ b/CRM/Mailing/BAO/MailingJob.php
@@ -248,6 +248,10 @@ public static function runJobs_post($mode = NULL) {
 
       $anyChildLeft = CRM_Core_DAO::singleValueQuery($child_job_sql, $params);
 
+      if (!$anyChildLeft) {
+        $anyChildLeft = self::queueMissingRecipients((int) $job->mailing_id, (int) $job->id);
+      }
+
       // all of the child jobs are complete, update
       // the parent job as well as the mailing status
       if (!$anyChildLeft) {
@@ -274,6 +278,75 @@ public static function runJobs_post($mode = NULL) {
     }
   }
 
+  /**
+   * Stopgap to find and enqueue any missing mailing recipients.
+   *
+   * This shouldn't be needed, but it's been reported that the initial mailing job sometimes misses recipients.
+   * This searches for any missing recipients and creates a child mailing job for them.
+   *
+   * @see https://lab.civicrm.org/dev/core/-/work_items/6678
+   *
+   * @param int $mailingID
+   * @param int $parentJobID
+   *
+   * @return bool True if a new child job was created for unqueued recipients, false otherwise.
+   */
+  private static function queueMissingRecipients(int $mailingID, int $parentJobID): bool {
+    $sql = "
+      SELECT mr.email_id, mr.contact_id, mr.phone_id
+      FROM civicrm_mailing_recipients mr
+      LEFT JOIN civicrm_mailing_event_queue meq
+        ON meq.mailing_id = mr.mailing_id
+        AND meq.is_test = 0
+        AND (
+          (mr.email_id IS NOT NULL AND mr.email_id = meq.email_id)
+          OR (mr.phone_id IS NOT NULL AND mr.phone_id = meq.phone_id)
+        )
+      INNER JOIN civicrm_contact cc ON cc.id = mr.contact_id
+      WHERE mr.mailing_id = %1
+        AND meq.id IS NULL
+        AND (mr.email_id > 0 OR mr.phone_id > 0)
+        AND cc.is_opt_out = 0
+    ";
+
+    $unread = CRM_Core_DAO::executeQuery($sql, [1 => [$mailingID, 'Integer']])->fetchAll();
+    if (count($unread) === 0) {
+      return FALSE;
+    }
+
+    $maxOffset = (int) CRM_Core_DAO::singleValueQuery("
+      SELECT MAX(job_offset) FROM civicrm_mailing_job WHERE mailing_id = %1 AND job_type = 'child'
+    ", [1 => [$mailingID, 'Integer']]);
+
+    $newJob = MailingJob::create(FALSE)->setValues([
+      'mailing_id' => $mailingID,
+      'job_type' => 'child',
+      'parent_id' => $parentJobID,
+      'job_offset' => $maxOffset + 1000,
+      'job_limit' => count($unread),
+      'status' => 'Scheduled',
+    ])->execute()->first();
+
+    $records = array_map(fn($row) => [
+      'job_id' => $newJob['id'],
+      'mailing_id' => $mailingID,
+      'is_test' => FALSE,
+      'email_id' => $row['email_id'] ? (int) $row['email_id'] : NULL,
+      'contact_id' => (int) $row['contact_id'],
+      'phone_id' => $row['phone_id'] ? (int) $row['phone_id'] : NULL,
+    ], $unread);
+
+    CRM_Mailing_Event_BAO_MailingEventQueue::writeRecords($records);
+
+    Civi::log()->notice("MAILING RECIPIENT IRREGULARITY FIXED: Mailing #{mailing_id} missed {count} recipient(s) in its initial queue. Additional job #{job_id} has been created to ensure the missing recipient(s) receive the mailing. Please report this on https://lab.civicrm.org/dev/core/-/work_items/6678 to help us track down why these irregularities happen in the first place.", [
+      'mailing_id' => $mailingID,
+      'count' => count($records),
+      'job_id' => $newJob['id'],
+    ]);
+
+    return TRUE;
+  }
+
   /**
    * before we run jobs, we need to split the jobs
    *
diff --git a/tests/phpunit/CRM/Mailing/BAO/MailingJobTest.php b/tests/phpunit/CRM/Mailing/BAO/MailingJobTest.php
index 85e9b1f1bb72..626a7417d6ad 100644
--- a/tests/phpunit/CRM/Mailing/BAO/MailingJobTest.php
+++ b/tests/phpunit/CRM/Mailing/BAO/MailingJobTest.php
@@ -16,6 +16,7 @@
  * @group headless
  */
 class CRM_Mailing_BAO_MailingJobTest extends CiviUnitTestCase {
+  use \Civi\Test\Api4TestTrait;
 
   /**
    * Tests CRM_Mailing_BAO_MailingJob::isTemporaryError() method.
@@ -40,4 +41,100 @@ public function testIsTemporaryError(): void {
     }
   }
 
+  /**
+   * Tests CRM_Mailing_BAO_MailingJob::queueMissingRecipients() stopgap.
+   */
+  public function testQueueMissingRecipients(): void {
+    $contact = $this->createTestRecord('Contact', [
+      'contact_type' => 'Individual',
+      'first_name' => 'Reconcile',
+      'last_name' => 'TestUser',
+    ]);
+    $contactID = $contact['id'];
+
+    $email = $this->createTestRecord('Email', [
+      'contact_id' => $contactID,
+      'email' => 'reconcile_test@example.org',
+      'is_primary' => 1,
+    ]);
+    $emailID = $email['id'];
+
+    // Create a dummy mailing
+    $mailing = $this->createTestRecord('Mailing', [
+      'name' => 'Reconciliation Test Mailing',
+      'subject' => 'Test Subject',
+      'body_text' => 'Test Body',
+      'status' => 'Running',
+    ]);
+    $mailingID = $mailing['id'];
+
+    // Create parent job
+    $parentJob = $this->createTestRecord('MailingJob', [
+      'mailing_id' => $mailingID,
+      'status' => 'Running',
+      'is_test' => 0,
+      'job_type' => NULL,
+    ]);
+    $parentJobID = $parentJob['id'];
+
+    // Create completed child job
+    $childJob = $this->createTestRecord('MailingJob', [
+      'mailing_id' => $mailingID,
+      'parent_id' => $parentJobID,
+      'status' => 'Complete',
+      'is_test' => 0,
+      'job_type' => 'child',
+      'job_offset' => 0,
+      'job_limit' => 10,
+    ]);
+
+    // Insert a recipient record into civicrm_mailing_recipients without queueing in civicrm_mailing_event_queue
+    CRM_Core_DAO::executeQuery("
+      INSERT INTO civicrm_mailing_recipients (mailing_id, contact_id, email_id)
+      VALUES (%1, %2, %3)
+    ", [
+      1 => [$mailingID, 'Integer'],
+      2 => [$contactID, 'Integer'],
+      3 => [$emailID, 'Integer'],
+    ]);
+
+    // Initial check: recipient is not queued
+    $reconciled = Invasive::call(['CRM_Mailing_BAO_MailingJob', 'queueMissingRecipients'], [$mailingID, $parentJobID]);
+    $this->assertTrue($reconciled, 'queueMissingRecipients should return true when unqueued recipients are found');
+
+    // Verify a new child job was created
+    $childJobs = \Civi\Api4\MailingJob::get(FALSE)
+      ->addWhere('parent_id', '=', $parentJobID)
+      ->addWhere('job_type', '=', 'child')
+      ->execute();
+    $this->assertCount(2, $childJobs, 'A new child job should be created for unqueued recipients');
+
+    // Get the new child job ID
+    $newJob = NULL;
+    foreach ($childJobs as $job) {
+      if ($job['id'] !== $childJob['id']) {
+        $newJob = $job;
+        break;
+      }
+    }
+    $this->assertNotNull($newJob, 'New child job found');
+    $this->assertEquals('Scheduled', $newJob['status']);
+
+    // Verify recipient was added to civicrm_mailing_event_queue for the new job
+    $queuedCount = CRM_Core_DAO::singleValueQuery("
+      SELECT COUNT(*)
+      FROM civicrm_mailing_event_queue
+      WHERE job_id = %1 AND email_id = %2 AND contact_id = %3
+    ", [
+      1 => [$newJob['id'], 'Integer'],
+      2 => [$emailID, 'Integer'],
+      3 => [$contactID, 'Integer'],
+    ]);
+    $this->assertEquals(1, $queuedCount, 'Unqueued recipient should now be present in event queue');
+
+    // Second check: no more unqueued recipients
+    $reconciledAgain = Invasive::call(['CRM_Mailing_BAO_MailingJob', 'queueMissingRecipients'], [$mailingID, $parentJobID]);
+    $this->assertFalse($reconciledAgain, 'queueMissingRecipients should return false when all recipients are queued');
+  }
+
 }