For the missing parts, we’d actually need to see the content of the AI file you’re trying to load to figure out why LightBurn’s importer isn’t getting it. There are some features in AI files that LightBurn doesn’t support, like patterned fills or clip masks, so it might be one of those.
The gaps in overlaps are because LightBurn uses an “odd/even” fill rule, meaning that each line encountered toggles the fill on or off, so when two shapes intersect like this, it toggles.
You can see this here too: Why do things disappear when I fill them, but not when I cut them?
To prevent this, make sure the design doesn’t have overlapped areas, and if you can’t fix that in the source software, select the parts that overlap and use the ‘Weld’ button in LightBurn to fuse the shapes together.