Toro Tube generating wavy heightmap - fix?

I'm terribly spatially dysfunctional (I have trouble visualizing things in space). I did major rebuilds of my Vcore4 500, including adding Mandala Rose Works joiners with a Toro tube. Pretty sure the Toro tube is bowed / U shaped. I'm now seeing wavy heightmaps. And struggling to understand what this translates too - Kapton tape on the gantry on the low sections? High? Or other? How does one fix this? Thank you!