Z Banding Issues?

Hello community, need your help. I noticed after a few prints on the same tall object, my prints started to have ‘wavy lines’ Anyone knows why? I’ve already done this

  • recalibrated a couple of times
  • cleaned the z-axis and applied grease
  • cleaned the x and y axis, and applied grease + WD40
  • ensured that the z-axis screws are not wobbly

I have no idea what’s going on, and it’s getting incredibly frustrating. Thanks in advance for your help!!

Image with the two objects - the left one is the problem. The right one was the expected results.