1212 CNC Potentially Bent Ball Screw?

Hello everybody, this is my first post in this forum!

I have purchased a 1212CNC router from China which I plan to manufacture my parts with. I have run into some problems which I can't seem to get my head around and request some help!

Ok, so my first problem has me thinking that there is a bent ball screw on the X-Axis. No matter what feed & speed combo I throw at it, there are marks on the surface (even when facing 0.1mm deep) at 10mm intervals. My ball screw is a 2510 which leads me to believe that a bent screw could be the culprit. I have tried adding a flexible jaw coupling, re-aligning the screw, and shimming the ball nut to no avail...

My second, larger problem, is that when climb cutting on the Y-axis (Y+) the spindle seems to 'Jump' through the cut, visibly shaking. I am aware that routers lack rigidity however this is a machine which should be more than capable of machining 6061 aluminum at the feeds I'm giving it:

RPM: 10,000
Feedrate: 1000mm/min
DOC: 4mm
Optimal Load: 1

This combination seems to be working well for very similar machines online however my machine prefers shaking itself to pieces!

Please let me know what you think, I'm at a point where I feel as though I've checked everything and just trying to find the cheapest upgrades necessary to make the machine perform better

You will probably have better luck over at the Zone getting help, not too many Chinese router owners here, if any.

If you buy cheap china shit, you should expect cheap china shit.

Me's would think checking a shaft for straightness is a rather elementary task for someone planning on manufacturing parts

Hey mate, an elementary task it is however I have already identified that it is bent. I am just wondering if it can cause the problems I am facing before replacing/straightening it out.