try to unset productId

app/Cron/BackupRemove.php

@@ -126,7 +126,7 @@ class BackupRemove extends Command
         }
         $whmcsParams = di('whmcsParams');
         $whmcsParams->setParams($params);
-        unset($this->vm, $this->api, $this->configuration);
+        unset($this->vm, $this->api, $this->configuration, $this->productId);
         $storage        = $this->configuration()->getBackupStorage() ? $this->configuration()->getBackupStorage() : 'local';
         $fileRepository = new FileRepository();
         $fileRepository->setApi($this->api());
@@ -193,7 +193,7 @@ class BackupRemove extends Command
                         $params
                     );
 
-        unset($this->vm, $this->api, $this->configuration);
+        unset($this->vm, $this->api, $this->configuration, $this->productId);
         $storage        = $this->configuration()->getBackupStorage() ? $this->configuration()->getBackupStorage() : 'local';
         $fileRepository = new FileRepository();
         $fileRepository->setApi($this->api());