I almost have identical noise coming from the same area under the car. Link posted below.
I checked the exhaust pipe and the brackets as well as the heatshield and all of them seem to be secured tight.
I am thinking of changing the starter to see if it is the culprit.
Side note: I changed my starter after it died with an aftermarket starter many years ago. It starts the engine just fine but could have the gear loose?
I also used a cheap endoscope to look at the gears from the peep window and the gears seems fine. I will also post a video of the gears.