Change staff and dynamics position

[Philippe Auclair]

Hi,

In the following example, in the piano left staff music, \clef "bass" is 
BEFORE \dynamicUp : the score goes completely wild ! (1st attached pdf).
If \clef "bass" is AFTER \dynamicUp, the score is correct (2nd pdf).
Is there an explanation?
Philippe Auclair

% This is the beginning of the piano part of
% Jules Massenet, Chansons des bois d'Amaranthe N°5, Chantez !
% Graver: Philippe Auclair
% If \clef "bass" is set before \dynamicUp, piano left staff is wrong
% If \dynamicUp is set before \clef "bass", piano left staff becomes correct

\version "2.20.0"
\include "italiano.ly"

PianoRightMusic = \relative do {
        \key sib \major
        \time 2/4

        \change Staff = "PianoLeft" \voiceOne fa8^.^^[
           \change Staff = "PianoRight" \oneVoice
           r16 <sib' mib sol>^^] <sib mib sol>4 ~
        <sib mib sol>8[ r16 <sib' mib sol>^^~] <sib mib sol>4
}

PianoLeftMusic = \relative do {
        \clef "bass"
        \dynamicUp
        \key sib \major
        \time 2/4

        \voiceTwo <fa, fa,>8^.^^ \oneVoice r8 \clef treble <do'' mib sol>4^^ ~
        <do mib sol>8 r <sib' mib sol>4^^
}

\score {
    \new PianoStaff {
      <<
      \new Staff = "PianoRight" { \PianoRightMusic }
      \new Staff = "PianoLeft" { \PianoLeftMusic }
      >>
    }
}