Adding letters/notes can indeed be a little quirky and frustrating. I find it best to work as follows
1: write the lyrics out in windows notepad (including all spaces/dashes/syllables)
2: record/write the notes into the Sonar midi track track that will trigger the lyrics.
3. Select all of the lyrics in the notepad lyrics file and copy them to the clipboard (control>a then control>c)
4. Open lyric view on theSonar lyric midi track, select all of the dashes, then paste the lyrics in from the clipboard (control>v).
Using this method Sonar will not add or take away any syllables from either the midi track or the lyric view. If you need to make corrections, select ALL of the lyrics in lyric view and delete them first (dashes will reappear to replace them), make any changes in the midi track using PRV to change trigger notes or the windows notepad file to change lyrics, then re-paste the lyrics as above.
Although a bit convoluted, once you get the hang of this method it is much faster than dealing with the unpredictable creation of notes and letters you are no doubt becoming familiar with when editing exclusively in lyric view.