you can adjust the strike of individual typebars by either filing or peening the ring-stop tab, file to hit harder & peen to lighten it. for your situation, you will want to file the ring-stop down a bit; make sure to tilt the machine up(or on its side) so the debris created doesn’t fall down into the pivot segment, then blow the area out with compressed air. if you go to Hobby Lobby or an RC model shop, you should be able to get a cheap set of needle files which will do the job; follow up with 600-800 grit sandpaper to remove burrs

roller pliers are for adjusting the height of individual letters(increasing the arc to lower & decreasing arc to raise, which in extreme case can then require adjustment of the slug to put it ‘square’ again relative to the platen) adjusting the strike for most models is done by either filing or peening the ring-stop tab near the base of the typebar(as is the case for OP’s smith corona)

Dolettersin alinesometimesstart nicely,thenrundownhill?Thiscan’thappenifyouuse theline-spacinglever,insteadofrollingthepaper throughwiththecylinderknob.Inthelatter case, the rollerthatlocksthespacingofthe linesmaycometorest on topofaratchettooth,insteadofsettlingbetweentwoofthem.Whenthemachinestarts, thevibration graduallyjarsthecylinderarounduntilitreachesitsnormal position—droppinglettersasitturns.

Check the alignment of the type by striking eachcharacter between the straight-sided letter "N"

One of the first thing I noticed was the rubber on this foot was sticking. This is the resting spot for the basket shift. Moving it up or down will adjust where the lower case letters strike the platen. I removed the old sticky rubber. There are two adjustments here, you can’t see the other one, but it’s looks the same. One is for lower case letters the other is for upper case. This is called the “on feet” adjustment. If you ever have the top of an upper case letter not imprinting or not level with the lower case letters, look at this adjustment. A good way to tell is to type HhHh, and see if the bottoms of the letters line up.