Upon opening the files, Luban 4.4.0 prompts me that both files appear to have errors, and would I like to correct them? I said yes.
Before slicing, zooming in on the bottom of LEFT, you can see the rings are just a bit proud. They’re not quite flush with the bottom. So the layer 0 is a bunch of rings and support material, and layer1 is the bottom surface. There also appears to be some weirdness with the meshes in one corner. I’m slicing at 40% scale at 0.2mm layers:
Layer0 preview:

Layer1 preview:

There’s also some weirdness at the top. Before slicing, the rings are open at the top. After slicing, layer14 shows the rings being covered over, which is why the rings are full of support material.

It appears to be a single layer at layer 14, as layer 15+ don’t go inside the rings again. That layer covers everything except a single ring in the corner. Layers 2-6 seem to be doing some odd things to the plus shapes. If you click on the layer slider, you can use the up and down arrows to move up and down a single layer at a time. I use that a lot when I’m evaluating models to see if they will need support or not.
I retried both without having Luban repair the models. That actually looks better. The layer0 mesh weirdness is gone, but layer0 is still just ring outlines and layer1 is the bottom surface of the model. The layer14 sheet across all-but-one rings still exists.
The two rings in the corner with the through hole connector have taller atomic logos inside the rings. I’m unsure if that was intentional or not.
If I slice using Cura, I get a warning that LEFT has some mesh issues and is not watertight. There are some random circles in layers 4-6, and this time the solid layer is layer16. So I think you’ve got some mesh errors in there that need to be fixed.
I’ve personally never done mesh editting, but if you search the forums for “mesh repair”, there are a lot of good posts. At my personal skill level, I’d probably just start from scratch again, but YMMV.