strange collision of note and clef

[hans]

In a piano-piece:
4/4 time
right-hand plays truplet over half-note, in problem case quarter-note
half-note.
left-hand plays eights, changing clef every quarter-note.
In the problem-case the clef is written over the preceding eight.

How to solve this problem.

code:
-----------

upper = \relative c' {
  \clef bass  
  \override Staff.TimeSignature #'stencil = ##f
  \times 2/3 {r4^\markup {\left-align  {\large Donker}} bes2} \times 2/3
{bes2 d4 }
  \times 2/3 {e,2 e4~ } \times 2/3 {e4 f2~\fermata }
   \times 2/3 {f4 \clef treble <d'' d' >2^\markup {\left-align  {\large
Molto Esspressivo}} }  \times 2/3 {<d d' > <fis fis' >4 }
  \times 2/3 {<gis gis, >2 <gis~ gis,~ >4 }  \times 2/3 {<gis gis, > <a
a, >2 }
  <cis cis,>2 \times 2/3 {<cis cis, >2 <f f, >4 }
  << {<c c,>2. } \\{r2 <d, gis>4}  >> r4
}

lower = \relative c' {
  \clef bass \override Staff.TimeSignature #'stencil = ##f
  
 s1 s1 \clef treble r4. gis'8 \clef bass c,,[ g'] \clef treble d'' gis,
\clef bass fis,,8 \clef treble cis''\noBeam c'! fis, 
<< {\clef bass fis,,8   [cis']  \clef treble c''! fis,} \\ { s8 s16 s
s4 } >>
f,8 c' cis b' \clef bass f,, [c'] \clef treble cis' b'
fis [c] \clef bass gis, d' <c' fis >4 r
}
----------

Hans