Okay, finally had some time to sit down and work on this.
C3 is replaced. I didn't notice any change in the vertical behavior, but I hooked up a source and it looks like the waviness is gone.
I've ordered a new C1. It turns out that the C1 I swapped in is a lower temperature rating than it expected, so I've sourced another and will see if that helps. Not sure it will, but maybe it will at least get rid of the buzzing that's come up.
I made another video to show where I am.
https://youtu.be/gIrCuJHy9OQ
Any thoughts on what I should check next?