I think I narrowed down these lines to a rotary module issue. like there’s a slip or something at each step. Has anyone else had these issues? Using 2w 1064nm laser on SS coated cups. Each image is either from Luban or Lightburn and both setup parallel along the Yaxis in the snapmaker 2.0 and the Ray.
Because you use the 2w IR laser, you use the latest firmware, right?
Yes I would assume both my machine have the latest firmware. Both were updated when I set them up recently.
I may imagine that - but looking on your first photo, I seem to notice the lines continuing in a second laser job above:
That would be a lot of conincidence - and might hint on some production residue from the making of the cups. You have the original in your hands - would you agree with my observation, or am I hallucinating? 
they are a little bit off . the top image was accidently defocused a couple mm. I feel like it has something to do with the rotary module but I don’t really want to mess with it, rip it apart or whatever. sometimes the lines are like 1mm apart and sometimes they are 1.5mm apart. I think depending on the diameter of the cup. I feel like it’s some sort of over lap each step. I’ve tried different line ints but nothing I’ve tried fixes it. These are 50x and 1000x zoom on the same area.
If you are still under warranty I would open a ticket:
https://support.snapmaker.com/hc/en-us/requests/new
Here is a topic about lost steps of the rotary:
Does the machine rotate, laser 20 lines (for example), rotate, and repeat?
Or does it rotate for every single laser line?
tool head moves along the y axis, the machine rotates ccw every single laser line
I don’t uses the rotary device but, how does it know the diameter of the cup?
in software you set the diameter
It seems to be a discrepancy between 1. the diameter setting in the software, 2. the diameter the machine is interpreting that setting, 3. the actual diameter of the cup, and 4. maybe also the position of the cup (the centre of rotation is not where the machine thinks it is).
I am thinking the software divides the image into small planar segments and projects the image segments onto an imaginary faceted cylinder. I believe the overlap would not occur if the cup was larger (leaving the diameter setting as it is) or the cup was raised higher.
If the diameter setting is correct to the cup size, a fix would be to reduce this setting to less than the cup actually is (after calibration to make sure the cup centre line is where it thinks it is in Z). This would be just a fix and this would not establish the actual cause of the discrepancy.
I opened a ticket and they asked me to do an engraving without the rotary to see if it still had the same issue. So I was able to get a couple extra pictures on the issue. Same cup, same settings. 600mm/min, 65% power, 0.04 Line Int, 4% OS. The closeups show the lines a little better because they are offset a bit.
Top Square 50x zoom
Bottom Square 50x Zoom
Top Square 1000x Zoom
Bottom Square 1000x zoom
Here’s another one, I’ve circled the start/stops.
I understand what you are saying with the small planar segments. If this was the case, the overlap area would have more uniformity to it. Segment A ends and then the module slips back and starts Segment B or Segment A’s 2nd last line ends and the Segment B’s 1st line starts or whatever that overlap transition area would look like.
Sorry, was offline for a few weeks - would you mind to share the GCode that produces the irregularities? I would be curious if it is perhaps a rounding error and the GCode commands are actually “slipping”. If not, I’d see how the same code behaves on my rotary - this might help to understand if it is a systematic issue or one of your specific module. What would be the diameter of the cup?
EDIT: And what firmware are you running your SM2 on?