When you move the type bar by hand, is it centered in the type guide, or rubbing on one side? And does it move freely with no binding?

Do you have any compressed air?  I was thinking it was sticking in the vibrator, but if you aren't seeing it being wedged in, or feeling resistance in the vibrator slot, maybe it is in the segment. 

If you raise the typebar by hand, is there a particular point in its travel where it gets stuck, or is it only when it strikes?
 

Now I recall some advice from Richard Polt's book, that worked for one of my typewriters. Press the key slowly, so the typebar moves much slower than with normal typing force. You should find it binding somewhere along its travel. I did this to all the keys of a troubling machine and was able to determine which ones were prone to binding, then thoroughly cleaned out the slots of the segments with degreaser.

Of course, every machine is different. Good luck.

Okay, I just ran into an issue on the little Smith-Corona Corsair I was cleaning up to sell.  The cent/@ key was sticking in a similar way.  And like your i key, it would stick up in the metal thing in front of the vibrator.  However, it wasn't binding in the metal thing (lets call it a type bar guide).  I lifted the type bar slowly and found that it was binding at the segment.  It seemed like it was binding on the left hand (or inner) side.   I looked in the segment and washed it out well with naptha, but it still bound up.  I tried poking gently in there to see if something was stuck.  It wasn't.  I put a little bit of oil in it to see if that helped.  It helped a little but it was still binding.  I then theorized  that the typebar was just a little bit bent right where it slots into the segment, causing it to bind.  I grabbed the type bar and gently bent it to the up and right.  That helped a lot, but it was still not quite freely moving, so I bent it just a tad more.  That cured it completely.

I'm not saying that's wrong with yours, but it's sort of the process I went through to determine where it was hanging up and how I approached getting it moving freely again.

I finally got the degreaser out today.  After the first spray, I found a few other keys that wanted to stick.  So, I gave the segment a good soaking.  I think I got some on the ribbon on the last spray.  oops.  Oh well.  I'm letting it sit outside until the degreaser stink is gone.  I hope this sorts it out.