I am playing a HLS stream with subtitles. However, on bitrate change, playback hangs.

I dumped the .dot file (see attached), and saw that text_sink pad of playsink was not connected.

Inside gstplaysink.c, following code is there:

      if (!playsink->text_sinkpad_stream_synchronizer) {
        GValue item = { 0, };

        playsink->text_sinkpad_stream_synchronizer =
            gst_element_get_request_pad (GST_ELEMENT_CAST
            (playsink->stream_synchronizer), "sink_%u");
        it = gst_pad_iterate_internal_links
            (playsink->text_sinkpad_stream_synchronizer);
        g_assert (it);
        gst_iterator_next (it, &item);
        playsink->text_srcpad_stream_synchronizer = g_value_dup_object (&item);
        g_value_unset (&item);
        g_assert (playsink->text_srcpad_stream_synchronizer);
        gst_iterator_free (it);

        gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (playsink->text_pad),
            playsink->text_sinkpad_stream_synchronizer);
        gst_pad_link_full (playsink->text_srcpad_stream_synchronizer,
            playsink->textchain->textsinkpad, GST_PAD_LINK_CHECK_NOTHING);
      }

Now, in case of dynamic pipeline switching playsink->text_sinkpad_stream_synchronizer will not be NULL but still below two lines 
need to be executed for its reconnection (as is done for audio/video pads):

        gst_ghost_pad_set_target (GST_GHOST_PAD_CAST (playsink->text_pad),
            playsink->text_sinkpad_stream_synchronizer);
        gst_pad_link_full (playsink->text_srcpad_stream_synchronizer,
            playsink->textchain->textsinkpad, GST_PAD_LINK_CHECK_NOTHING);