Script to trigger the issue

script.sh

#!/bin/bash

file=$1

while true
do
  # get the window id
  WID=`xdotool search "mpv" | head -1`
  if [ -z "$WID" ]; then
    mpv $file &
    # got to wait for mpv to start before doing anything again
    sleep 1
    continue
  fi
  
  val=`shuf -i0-1 -n1| bc`
  if [ $val -eq 0 ]; then
    xdotool key --window $WID Up
  else
    xdotool key --window $WID Down
  fi
  
  dmesg > dmesg.txt
done