Difficult to understand debugging output

[sixtyfive]

With this code

Numo.gnuplot do
  debug_on
  set :title,   'Letzte Stunde'
  set :term,    'pngcairo' # size 1024,576' # 16:9
  set :output,  'hourly.png'
  set :xdata,   'time'
  set :timefmt, TFMT
  pp [x[0], y1[0]]
  pp [x[1], y1[1]]
  pp [x[2], y1[2]]
  plot x, y1
end

I'm getting this output

<set title "Letzte Stunde"
<set term pngcairo
<set output "hourly.png"
<set xdata time
<set timefmt '%F %T'
["2020-10-31 18:00:25", 0.3148651123046875]
["2020-10-31 18:00:26", 0.310211181640625]
["2020-10-31 18:00:27", 0.28819020589192706]
<plot '-' 
<"2020-10-31 18:00:25"
<"2020-10-31 18:00:26"
<...
<2.654648
<e

and then running it a second time, the last two lines change to

<3.702583
<e

and I'm having trouble using that info to get to the bottom of why gnuplot hangs indefinitely. Is there a way that instead of the three dots I could make numo-gnuplot show what would actually have been there?