playbin produces two about-to-finish signals with ogg sound files

With an ogg sound file, the following program gets about-to-finish twice. A sound file with the same data but some other codec (wav, flac, mp3) results in only one.

`

import os

import gi
gi.require_version('Gst', '1.0')
gi.require_version('GLib', '2.0')
from gi.repository import Gst, GLib

WORKING_DIR = os.path.dirname(os.path.abspath(__file__))

class PlayEngine:
    def __init__(self):
        Gst.init(None)

        self.playbin = Gst.ElementFactory.make('playbin', None)
        self.playbin.connect('about-to-finish', self.on_about_to_finish)

        self.bus = self.playbin.get_bus()
        self.bus.add_signal_watch()
        self.bus.connect('message::eos', self.on_eos)

        uri = 'file://' + os.path.join(WORKING_DIR, 'demo.ogg')
        #uri = 'file://' + os.path.join(WORKING_DIR, 'demo.mp3')
        self.playbin.set_property('uri', uri)
        self.playbin.set_state(Gst.State.PLAYING)

        self.loop = GLib.MainLoop()
        self.loop.run()

    def on_eos(self, bus, msg):
        print('Quitting on eos')
        self.playbin.set_state(Gst.State.NULL)
        self.loop.quit()

    def on_about_to_finish(self, playbin):
        print('In on_about_to_finish')

play_engine = PlayEngine()

`

demo demo

I am on Kubuntu 19.10 with plugins base 1.16.1-1.