I have exactly the same artifacts on my Tevo Little Monster, also with nimble. But i tested with a BMG and the artifacts are the same. I changed everything on this printer instead of the beams and the heatbed and still can't get rid of it.
Running now Duet2Wifi, Nimble, Smart-Effector, 0.9° stepper, Magballs, Linear-Rails and Meanwell powersupply.