Faulty behaviour prawn with page numbers (repeatable content) & transactions (with page changes)

gistfile1.rb

require 'prawn'
require "prawn/measurement_extensions"

f = File.open('repeater.pdf', 'w')
Prawn::Document.generate f, page_size: "A4", margin: [2.cm, 1.cm, 2.6.cm, 1.cm] do |pdf|
  pdf.text "Some title"

  pdf.text "x\n" * 40

  pdf.start_new_page
  pdf.text "Some other title"
  pdf.text "x\n" * 40


  pdf.start_new_page
  pdf.text "Page with transaction"

  pdf.text "x\n" * 40
  p = pdf.page_count

  drawn = pdf.transaction do
    pdf.text "xy\n" * 30

    if pdf.page_count != p
      pdf.rollback
    end
  end

  if !drawn
    pdf.start_new_page
    pdf.text "Contd..."
    pdf.text "xy\n" * 30
  end

  pdf.start_new_page
  pdf.text "Last Page"
  pdf.text "x\n" * 40

  
  
  pdf.repeat(:all, :dynamic => true) do
    pdf.canvas do
      pdf.text_box "#{pdf.page_number} / #{pdf.page_count}", at: [pdf.page_number * 1.cm, 2.cm]
    end
  end
end