[Doanster]

It's not the nut that holds the spring/strut combo in place to the car. It's the top hat nut that holds the spring in place. The force of the spring pushes against this hat. When you go over, say, a speed bump, the spring compresses and if the retaining but isn't tight, there's a tiny bit of free play allowing the hat to move. Once the spring releases after the bump, it'll push the hat back up thereby causing the clunk.
So have your guy tighten that but again on the car. If the noise is still there, I'd have him pull the spring/strut assembly, compress the spring, then fully tighten the nut before decompressing the spring.
As for the dash cam, we know the writing on the wall. The dealer will use ANYTHING to claim that it was the fault of something we installed. So, I'd take a couple days and try all the coding reset, etc. first to see if things get resolved. If the dealer is your last resort, I'd unfortunately bite the bullet and remove the dash cam. V1 I'd leave in place as they're more familiar with it and it's only a hardwire pwr install. The dash cam ties into the screen so they can claim you messed with the iDrive system.