Tie question.

[Hwaen Ch'uqi]

Greetings All,
          I am attempting to tie two notes of an arpeggiated chord into the
chord proper. However, one of the ties appears more as a tiny dot
rather than a curve. Can anyone explain the reason for this and offer
a solution? Please find the code below.
          Many thanks.
Hwaen Ch'uqi

\version "2.14.2"

\score{
  \new Staff{
    \key f \major \time 2/4 \clef treble \relative{
      \tieDown
      \set tieWaitForNote = ##t
      \grace {cis16[ d~ g~]} <bes g d>2
    }
  }
  \layout{
  }
}