Grace note position and time signature changes

[David Santamauro]

Hi,

The following snippet produces some strange results:

\version "2.22.2"

\include "english.ly"

tt = {
  \time 4/4 s1 s1 s1
  \time 2/4 s2
  \time 4/4 s1
  \time 2/4 s2
}

\score {
  <<
    \new Staff {
      \relative c' {
        << \tt { R1 R1 a1 ~ a4 r4 R1 R2 } >>
      }
    }
    \new Staff {
      \relative c' {
        << \tt { R1
          \grace { d16 d d } d1
          R1
          \grace { d16 d d } d2
          R1
          \grace { d16 d d } d2 }
        >>
      }
    }
  >>
}

I don’t understand the differing behavior in mm 3-4 and mm 5-6. Is there a way 
to force the grace notes past (to the right of) the time signature?

Thanks