That does look a lot worse than either of my printers. The only silk I have is a tri-color; I might print a VFA with that to try to accentuate the artifact though it might end up looking a bit strange in other ways. I usually up the print temperature on most PLAs to maintain a shine at high temp, but that depends a lot on brand. My usual stuff I print at 240C, and I suspect you can go higher. I would recommend always printing with the cool plate if possible, since the lower chamber temperature can help reduce the likelihood of heat creep.
I have some horrible ideas that would give a few of the motion control engineers a heart attack, but they may help if you’re primarily targeting low speed prints.
At this point I actually think this might be characteristic of ALL printers. Note that we are NOT talking about z-wobble. paykoman84 / frank.d, that doesn’t look that great but this thread is about waviness in the other direction - VFA / ringing artifacts are waviness back and forth or left and right, not up and down (in XY not in Z). The crazy thing I’m going to tell you is you should try turning down the speed and see if the z-wobbliness goes away (could be due to insufficient cooling)