2018 Crosstrek making a bottoming out thumb noise in DF assembly when going over very small things

I just got Subaru 2018 Crosstrek Premium a week ago and traveled a couple minor dirt roads. In my drivers side axle wheel area I am getting a loud thump that sounds like bottoming out, it is loud and startling, look a rubber or wood mallet hitting something or maybe like a large thing being kicked up and hitting the vehicle. It happens when going over with the drivers side front tire very small rocks that stick up out of the road not very very far in the 2-3 inch range or well within the travel of the suspension. The rocks ar not coming loose to hit anything. It is only on the driver front assembly. It does not happen when going over dips or things. the vehicle drives fine, no pull, no noises other then this. No warning lights.

A visual inspection climbing under the vehicle reveals nothing. No bad bushings, no unusual wear points or anything that seems detached or loose. My best guess is that it is in the strut. I am taking it to the dealer to have them look at it and hopefully repair it. My feeling is that they may be clueless. I am hoping that someone else has had this problem and been able to remedy, so that I can go into the dealer with some kind of clue what it may be.

So Subaru owners have you had a similar clunking sound on your vehicle? If so what was the problem?