The forum won’t let a new member upload images or .skp files until they have had a few posts accepted (it’s that way to keep spam robots out). So, until you pass that mark we will have to discuss your issues with just words. It’s harder, particularly since as you note terminology may be unclear. Images and explicit work with a model is much easier!
What you describe certainly sounds like the results of inappropriate use of tags. The tag applied to a group or component will show/hide its contents regardless of how they are tagged. But also conversely: turning off a tag that is on an object’s contents will make them disappear regardless of what tag is applied to the object itself. That sounds like what you are observing.
Here’s the standard advice for safe use of tags:
- Think of tags as markers you attach or apply to whole objects (groups or components) to control visibility, not to the primitive geometry (edges and faces) that you use to draw those objects’ contents.
- Always leave “untagged” as the active tag (the little pencil icon in the tags window), which will cause any new edges and faces you draw to be untagged.
- Never assign other tags to edges or faces. Create groups or components from them and attach a tag to the group or component as necessary.
The way to fix your problems is to open each object for edit, select all, and choose untagged in the Entity Info window. If you do this to a component, it will also fix all other instances of that component. You can select an object to edit using the outliner, but it doesn’t provide any means to change the tags.
There is a behavior that many of us regard as a bug: if you explode a group or component that has a tag, that tag is then applied to all its exploded contents - both nested objects and primitive geometry. The tag should have only carried over to the objects. This behavior was implemented very early in the life of SketchUp, when people were still thinking of tags as being the same as organizational layers and wanted to avoid losing that organization, even for edges and faces. But tagging primitive geometry causes other issues in SketchUp because it does not prevent edges and faces from sticking to each other or intersecting - even when some of them have a tag that is not visible. It is only rarely necessary to explode a group or component to fix issues. Open it for edit and make the changes directly.