I've observed that upon initiating shutdown my grill will initially dump the last bit of pellets in, but very quickly begins reversing the auger. If you have observed 9 minutes of continued feeding, I'd suggest contacting support. That doesn't seem correct
Nine minutes does seem like a long time to continue to feed when shutting down but I’ll admit I’ve never watched that closely. I want to say it starts reversing pretty quickly but I could just be remembering the fan spinning up to burn up the remaining pellets in the firepot. I’ll try to remember to pay more attention next time I shut it down (if I can remember).