How do you fix one letter that prints lower than the rest?

Gamsol odorless mineral spirits does work. Using it requires several applications. I use it exclusively on all my typewriters.

I recently had this same problem and found a way to fix it. The ribbon reverse mechanism involves a rod with toothed wheels on both ends. This rod shifts left and right with the ribbon reverse lever. If the toothed wheels are not aligned with the cogs that turn the ribbon spool spindles, the ribbon won't reverse. The toothed wheels have small set screws that can be loosened so they can be moved to align with the spindle cogs. There are two pieces associated with each toothed wheel.  You have to moved both of them together.  You have to adjust, then test, then adjust, etc.

I the ribbon is not moving at all, check the PhoenIx Typewriter's YouTube video:https://www.youtube.com/watch?v=13nRoVuDdNY

Has anyone had any experience doing this? I have one letter that types lower than the rest, and I was wondering if using a keylever plier will fix it?

My only experience with Triumph typewriters is a 1938 Norm 6. One of the best typewriters in my collection and highly recommended. I would assume the Perfekt of that year would be of similar quality.