Sorry for super late reply, never noticed I got this private message.
Spot welding significantly reduced the noise (less frequent, quieter, and required a lot more torque in chassis to generate noise). Weary of revisiting the dealer and getting more welding, I figured out the plastic trim next to the seat was perhaps rubbing against the C-pillar window glass. I wedged small pieces of foam and the noise went away. Hopefully you have figured out a better solution to your noise.