SolidSolver: The form has been 'intersected'.

moot

I created the components from the same source and made minor changes.
One has two ‘flats’, the other one ‘flat’.
I run Solid Inspector2 on both and they come up ‘No errors, shiny”
Running SolidSolver on Main Center Rib comes up ‘The Selected GROUP/INSTANCE is already a 'Solid' !’
Main Rib Center.skp

Running SolidSolver the Outboard Main Rib ‘This seemingly 'Solid' Selected GROUP/INSTANCE 'intersects' itself !’. SolidSolver then removes everything except the guide points...
Outboard Main Rib.skp

I’ve spent hours trying to find anything wrong…
Although the Entity info says it is a Solid Component in the model (and the exported .stl prints on the 3D printer) it is just bugging me!
Also, Sketchup will BugSplat! if I check and there are multiple components in the model.

What am I missing?

TIG

SolidInspector2 does not check for self-intersecting geometry.
This can cause issues with 3d-printing - if for example a face is penetrated but not properly intersected.

SolidSolver does check for this self-intersection, and highlights the offending geometry.
I then tries to fix it, but in your case it fails.

In your case it's because there is some geometry which seems to exactly overlay others, and the intersect operations picks that up.
It's unlikely to affect 3d-printing, but SolidSolver balks at it.

A simple fix for this is that once SolidSolver fails, and reverts as it was, you simply edit the component/group, edit > select all and use the right-click > context-menu > intersect > with context.
If there were nothing to fix it'd tell you, but in your case that overlaid geometry is fixed.
If you exit the edit and retry SolidSolver it now reports as a 'Solid', because the rogue geometry has been resolved.
You can see this if you edit the component before intersecting - select-all and in Entity Info note the entities count.
Now do the intersection and reselect-all and in Entity Info the count goes up as a few extra faces are created by the intersection...

moot

Thank you TIG.
I didn't notice any highlights of the offending geometry.
Is there any other tool that can find the offending intersected geometry?
I'd like to know how it actually happened to being with, for future reference...
Anyway, thanks again for concisely explaining how to fix the issue.

p.s., I still get SketchUp Bug Splat if I put two of the same component in model. Does not happen if there are two different components, i.e., Main Rib Center & Outboard Center Rib.
I sent a Bug Splat report, Crash Report #73801. No response yet...