Problem when slice STL

Hey, I have problem when I try to slice the stl, some pieces are practically missing, can you help me?
I had to upload the files to mega because they are too large… (42.78 MB file on MEGA)

This is the result:

As far as the SketchUp model is concerned, there’s only one solid object, that’s the spoiler. Looks like your slicer software is trying to fix the rest of the model and is unable to do so. If the entire model was made of solid groups/components, I expect you wouldn’t have any problems. Go through the SketchUp model to clean it up and make solids.