The first thing would be to verify whether it's the actual type slug that is low in the type bar, or if it's the type bar that is bent out of shape. The latter scenario is the more common one. And how low is "a little low"? Unless it's really exaggerated I would suggest leaving it alone, but some typewriter owners are really bothered by any imperfection and won't rest until all the type is perfectly lined up. I only begin bending bars if it's an extreme case and the small stuff I leave as a signature of the machine.

If the body of the 'g' is in line with the other characters it's very possible that the type head is bent forward. If the body is low on the baseline then it could be that the type bar is out of shape or, as you suggested, the slug is not correctly position on the type bar. If you could post a type sample and a photo of the slug it would help to pinpoint the problem.