Un-shielded magnets can themselves be the issue as the magnetic field extends above the magnets and can interfere with anything electrical moving rapidly through it, You can find shielded magnets or wrap the top of the magnets you have in shielding.
Those are some big magnets, so likely they are causing issues as @rbtdanforth noted. Did the other two rows in the center of the leather have this issue, or just the outer row?
You may also have a lot more consistent results making a boat load of the hold down pins from scrap med maple ply or draft board (in free designs section) and pin the edges of the leather down–not sure what is underneath the leather–you should be fine without it. Recommend doing a row, put more pins on those new edges to help keep the center of the leather tight & flat.
They’re thick but they’re standard magnets - the ones that really need to be watched are the rare earth neodymium magnets. They are many times more powerful than ferrite magnets. One that thick would not come off the honeycomb bed (I use them on the Redsail to hold down qtr inch or thicker material because it doesn’t have the head fans that the GF does - they’ll dewarp badly bent thicker plywood.)
Is this PG leather? Is it happening on several pieces? Is it possible that the leather isn’t a consistent thickness across? If it’s thicker on one side than the other, that could account for some of what you’re seeing.
If you have some draft board that is not warped I’d try the same engrave on it and see if there is horizontal fading. I’ve had leather laid flat on the crumb tray where the thickness of the leather varied enough across about 12 inches of hide that the cut didn’t go all the way through.
The thickness of the leather matters on an engrave because the top of the leather is further away, or closer, to the laser head. As the laser beam is cone shaped, your leather could be intersecting it at different points even laid flat. This will result in the power of the laser beam being spread over more area for some engraves and less area for others.
I discovered that it was similar ferrite magnets that were stopping my head fan. They may be less powerful but they still throw a sizable field probably larger if less intense than a thin more intense neo magnet of the same pulling power.
I’m sorry about the trouble with your engrave results. I see you’ve already received some excellent information from our other community members. Thanks folks! It’s correct that variations in thickness or material which isn’t flat can impact print results. I also extracted the logs from your recent prints and noticed that a manual height was entered for the material thickness. As a next step, I would recommend trying the Set Focus tool.
The Set Focus target allows you to select an area to take a precision measurement of the material’s height using the red dot in the printer head. Use Set Focus and place the focus area on the material, so it’s not near an edge. Then watch to make sure the red dot hits the material.
Please let me know if the above improves your print results. Thank you!