Going to need a bit more information to offer you help.
Please provide a more detailed description of what this means. We don’t charge by the word so uses as many as you think would help us “see” what you do. Show picture for what you did and what you expected, along with the results and we can go from there.
First, I have updated your profile so you can post more.
Next, you mention C3D but you haven’t shared what firmware you are using so I’d need to know that. I would also like to know what cut settings you set for this and how does this look in the ‘Preview’ window?
You also mentioned that you are getting an error when trying to generate this file with Slicer for Fusion 360 (formally AutoDesk Make123). Please explain as the provide direct output to DXF and PDF without the process you described above. Both are directly supported in LightBurn.
When LightBurn connects to your system, a “hello” type message should display in the console window identifying the firmware (and for some, the version as well).
Please post an image showing this.
As for AutoDesk, I am not a user of TinkerCAD so I can’t offer you any help there. I use Slicer for Fusion 360 for this type of work which does not require me to log in or be online.
If the preview is jumping around like that, instead of treating it as a single connected design, select everything, un-group it (Ctrl-U) then use the auto-join tool (Edit > Auto Join, or Alt-J) to connect the shapes together.
I would also remove ‘Order by Priority’ and ‘Order by Group’, and turn off ‘Reduce Direction changes’ at least, until you properly understand what they do. Just turning on everything isn’t always the best idea.
As a starting point, skip trying to cut the complex shapes, and start with something simple and known, like a circle and a square, maybe with some simple text, and see how those come out with the settings chosen. From the image of the cut you’ve displayed, it looks like you could have a loose belt or lens, or your acceleration or speed settings could be too aggressive, but since the shape you’re cutting is wobbly to begin with, it’s hard to see what’s from the original shape and what’s erroneous output.
It looks like your hardware settings are incorrect. If you are trying to accelerate or move too fast, the stepper motors will skip.
The settings I’m referring to are stored in the config.txt file on the SD card of your Smoothieware device. Acceleration might be too high and require tuning, and it’s also possible that your motor current needs to be set higher - with the LaserBoard the motor current would be a setting in the config file.