What’s up with this ballscrew?

Hey all, I have a 440 from 2016 and though I push a bit further than what is to be expected of a little 440, she serves me well. I had an indicator on the spindle/head and was moving Z axis up/down. I was seeing a pulse on that axis. I put the indicator on the ballscrew and found the exact same pulse (jump on indicator. I am trying to get to the bottom of this anomaly so giving this new forum a crack at it. I know the Z axis needs to be squared up, not sure what that entails exactly, but it’s more the pulse that is in question.
Thank you!

Screw

Spindle

If you have a long reaching magnet tool, try running it along the ballscrew. I was seeing some “crunchiness” in some areas and it turned out to be some small ferrous chips / dust on my ballscrews left over from the factory.