Hi,
I’d start by cleaning up the model.
You have reversed faces, internal faces, and stray edges still around… as well as 147 guide points set in place.
The Fix:
Reverse Faces: reverse them back via the reverse face command
Internal Faces, and Stray Edges: can be selected and deleted.
Guide Points: run the Delete Guides command.
This can all be automated with the ‘Solid Inspector 2’ extension. . . but you should at least get familiar with fixing things manually, before leaning too much on an extension to bail you out of trouble. (the idea being that manual know how makes you a better modeler).
Get in the habit of selecting your raw geometry, and grouping it together. . . from there (while its still selected) look at the ‘Entity Info’ results. You want to see it’s classification read as a ‘Solid Group’, and not just a ‘Group’.
Also look at the ‘Statistics’ data that’s reported in the ‘Model Info’ window. That will get you a good idea as to the full contents of your model… although this doesn’t necessarily pinpoint problems the way that ‘Entity Info’, and the results from the ‘Solid Inspector 2’ extension do, it’s just extra info that can sometimes help you gain some insight into your models.