Just got my 2019 back from the dealer after 19 days troubleshooting this same sound. It turns out the IWE actuator broke and hub bearings were shot. They actually said it looked like whoever replaced the hubs did a poor job and broke the actuator…or that it was in an accident. Glad they serviced it under warranty.
I bought the truck from my 68yr old father who babied it, drove it to/from the office, never wrecked it, and always had the Ford dealer in Boerne, TX service it. Truck has 50k mi on it and all of the receipts/records cover basic maintenance. Seems like the IWE system may still be something to keep an eye on with the Gen2s like it was with my 2014, and if you have a metallic sound like OP posted at low speeds get your hubs checked out.