Engraving circles

Sorry if this has been sorted out or explained before but couldn’t find anything on this subject. I have had lightburn for over year and working fine, the only issue I have found is when I engrave a circle band, made in lightburn, the left side of circle starts to engrave like normal. The problem is the line is thinner then the rest of the circle. I have attached a pic to better explain it.

Everything else cuts fine just issue with the circles on cups. You can see that for some reason it flattens the circle edge. I also added pic of file. Ignore the tape wrinkle it’s on a test cup that I did just to show what happens.

What sort of engraver are you using? I assume you are using some sort of roller to ensure the cup rotates under the laser and therefore the laser is always engraving at the highest point on the cup. It almost looks like this is distortion from the curvature of the cup and as if you are not rotating the cup under the laser but moving the laser over the cup. Like in the image below, is the laser always in the center and the cup rotates under it or does the laser move left to right and the cup stays stationary?
If the laser is moving left to right here then that could account for the circle getting thinner at the far left and right.

It’s a Omtech Chinese laser. Yes I have a roller and the laser just moves on x axis while roller rotates on y axis. I thought about that too but when gets to the end of the circle design it engraves it fine. So not sure if it just isn’t rotated enough or starting late.

I am really new to this and don’t have a roller yet but it really seems like maybe the roller diameter or object diameter is slightly off. hopefully if that is not it someone with more experience is able to help you out.