Edges disappear or reappear when displaying new edges

# Display a large number of lines

#Category: Visualization BUG "invisible lines"
#Title: Display a large number of lines

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vinit View1 w=1024 h=1024
vsetdispmode View1 1
vtrihedron trihedron1
vsize trihedron1 400
vclear

#vtop
set scale 0.1
set vpprojx 0.0
set vpprojy 0.0
set vpprojz 1.0
set vpupx 0.0
set vpupy 1.0
set vpupz 0.0
set vpatx 4995
set vpaty 500
set vpatz 0
set vpeyex 4995
set vpeyey 500
set vpeyez 0.0001
vviewparams -scale $scale -eye $vpeyex $vpeyey $vpeyez -at $vpatx $vpaty $vpatz -up $vpupx $vpupy $vpupz -proj $vpprojx $vpprojy $vpprojz

set NB 1000

proc draw_lines {{distance 10.0}} {
  # set colors to corner spheres
  for {set i 0} {$i < $::NB} {incr i} {
    set x [expr $i * $distance]
    set ya 0.0
    set yb 1000.0
    set z 0.0
    vertex v1 $x $ya $z
    vertex v2 $x $yb $z
    edge e$i v1 v2
    vdisplay -update e$i
    puts "$i: $x $ya $yb $z"
  }
}

puts "Start test lines"
draw_lines 10.0
vfit