Clunking noise over rough pavement

[NYC-SE]

Recently my Yaris has developed a clunking noise while driving over rough pavement. To me it sounds like it is coming from the passenger side front suspension. It is an intermittent problem and does not always occur. It is more likely to occur if one or more of the following factors are present:

low ambient temperature
long time since car was last driven
slow speeds (under 35mph)
while driving on slight uphill grade
while turning

But as I said it is an intermittent problem. All of these conditions can be present and it will not happen. Likewise it has happened when none of these condition are present.

I can not get the car to make this noise by turning the steering wheel while stopped or by pushing down on the corners of the car while parked. The shocks rebound normally in that case.

Car drives the same as day one. No change in road feel, no shimmy or vibration at speed, tracks true. Handles, brakes, and steers as always.

I have crawled under the car, removed front tires and can not see anything obvious. I retorqued sway bar end links, strut bolts, caliper bolts. All were tight, wrench clicked at recommended torque. I did not put a wrench on every suspension bolt, but those I did were tight and all I could see looked good. So maybe it's not the suspension?

This is a 2014 SE model with a little less than 18K on the odo. I would not expect suspension damage at that mileage but NYC roads are pretty bad.

The car is still under warranty and I will bring it in sometime after the holidays but I would like to have some idea of what the problem is before I let them have a crack at it. The intermittent nature of it worries me. Based on prior experience with other vehicles I fully expect that when I do bring it in the car won't make any noise and the dealer will say everything's fine. I don't want to play that game. So if anyone here has had a similar noise if you would be so kind as to tell me what it turned out to be it would be appreciated. Even though this is a 3rd gen car the suspension is mostly the same as 2nd gen so 2nd gen owners please feel free to weigh in.

P.S. I know the first response is going to be post a recording of the sound. I've tried to get it on camera to no avail. I would like some proof for the dealership as well but the intermittent nature of it requires that I constantly drive with my phone in my hand. I got pulled over last week for that. Luckily the cop was nice and let me go with a warning.

Anyway the sound is best described as a "clunk". It is NOT a "clang" or a "bang". It is NOT a sharp metallic sound. It is definitely not normal. Hope that helps.