I'm trying to combine three solid groups using the Outer Shell tool. I know they're solids because I checked using the Entity Info box. They must be solids after being combined because I need to 3D print this model, but they end up as nonsolids. I have spent hours wracking my brain trying to fix this and I can't seem to do it, as a new Sketchup user. Any ideas? I tried using the Solid Inspector, but its results don't make any sense. The objects have lots of curves, and I think it might be that the tiny faces are causing problems, but I'm not sure.
I attached the model so that you can understand better, I can't really explain it well.