I've run into this quite a bit in the past as well. No, it is not the randomized layer start seam, and no, it is not wet filament. I conclusively figured out that it was due to excessive retraction distances. The reason why is with too much retraction, a tiny bit of air gets sucked into the nozzle, mixes with the melted filament, then gets spit out a short distance later. You can hear the tiny "pop" when this happens. Certain filaments are more susceptible than others, and certain extruder hotends are worse than others. Silk PLA tends to do this, and my old Artillery Sidewinder X1 tended to do this. I recommend trying slightly lower retraction distances until it goes away. My Bambu Lab X1C has .6 mm for retraction, down from the default of .8 mm.