HEAD tty seems to drop characters

I run a screen(1), where I tried to copy large portion of output and
paste it into vi. This resulted in the loss of the characters at random
points inside the pasted text.

See below:
original
...
  pango-1.24.4 needs updating (port has 1.24.5)
  policykit-gnome-0.9.2_1 needs updating (port has 0.9.2_2)
  poppler-gtk-0.10.6 needs updating (port has 0.10.6_1)
  postgresql-client-8.3.7 needs updating (port has 8.3.7,1)
  postgresql-contrib-8.3.7_1 needs updating (port has 8.3.7_2)
...
pasted
...
  pango-1.24.4 needs updating (port has 1.24.5)
  policy8.3.7 needs updating (port has 8.3.7,1)
  postgresql-contrib-8.3.7_1 needs updating (port has 8.3.7_2)
...

The effect is reproducable. System is some days old HEAD, r196002.
I think this is quite critical for 8.0.