Text is tied to a certain instrument track and a position. If you later decide to enter more tracks at the top of the score, the track with text gets pushed down, and text appears to be lost.. When you first enter text. there will be a little dotted line showing you.
If this happens, look at event list on right side of main melody, shut off display to noes, CC's etc, you will then see the text. My fast and dirty way to fix is delete, and retype making sure it is tied to the top instrument track. Perhaps, cut and paste work also, never tried.
The score editor is VERY old code, not much has been done to it, because of it's complexity. It is not as elegantly written as new code. However if you take the time to figure out it's secrets. It is quite flexible. And contrary to opinion is is used by a fair amount of composers to make charts for sessions. Really formal scores of course use Sibelious or Finale. They are the most powerful. But many people are content to use Logic for quick making of charts
MacPro 2015 12 core - 64 gig of ram
Logic Pro 10.6
RME fireface 800, Genelec 8040A's
Genos, Montage,Motif XS Rack, Korg M3, Intrega 7, Falcon UVI, Kontakt, u-he, musiclab
Kontakt, UVI, U-he, Music Lab- Modartt
Kontakt and UVI libraries, U-he, Madrona Labs, Music Labs, Serum, Synthmaster, Seaboard Rise, SWAM
SampleTank,Falcon,UVI, A.I.R. MusicTechnologies