There does seem to be a rough edge here. Basically, when you enter a lyric and hit Space, the lyric’s underlying length is extended to (I think) just before the start of the next note. In effect, that “uh” is 19 crotchet/quarter beats long, but a rule under the hood tells the extender line to only show for ~5 beats.
Before copying, select the (“uh”) lyric and type Shift-Alt-Left Arrow repeatedly until you see the lyric extender line shorten. If the rhythmic grid is set to crotchets/quarters then it’ll be 15 times (though obviously you can just hold down Shift and Alt and then hammer the left arrow). Once you see the lyric extender line visibly shorten, either hit Shift-Alt-Right once or hit Cmd/Ctrl-Z once. Then you’ll find that copying and pasting, repeating, alt-clicking the two bars will work just fine.
Alternatively you can select bars 15 and 16 and hit Delete or Backspace. This will allow alt-clicking or copying and pasting to work correctly, but not repeating (as the lyric will still technically be longer than the first two bars).
I know that the underlying behaviour has been described as intentional before (here, for instance), but in this particular case it feels like a bug to me.