Loading components from files in with the Ruby API is a mess. SketchUp replaces an existing definition rather than loading a new one if the associated path is the same. It also refuses to reload in some situations. I can’t even remember what it does as it doesn’t make much sense but I think it happens when the components hasn’t been modified since it was loaded, regardless of whether the external file has been modified. Workarounds consist of making arbitrary changes to components, e.g. draw a cpoint, and save out files to temporary locations just to disassociate them with the load path.
Bugtracker issue: Component loading and reloading · Issue #50 · SketchUp/api-issue-tracker · GitHub