playbin3 hangs on stream change

[Robert Tiemann]

Hi!

I have discovered that playbin3 has a problem with skipping to next
stream in gapless mode. If you try to skip near the end of the current
stream, then it will just hang.

This issue can be reproduced with gst-play-1.0 (GStreamer 1.18.5 as
well as latest Git version) as follows:

1. Run gst-play-1.0 --gapless --use-playbin3 *.mp3
2. Play or fast forward to near the end of the first file using the
    right arrow key.
3. Wait until the player says, "About to finish, ...".
4. Quickly hit > to skip to the next stream.
5. Player says, "Now playing" and "Prerolling...", but that's it.
6. Hitting > again skips to the next stream, but it won't play either.

It works fine if you omit the --use-playbin3 option. Is this a known
bug?

Best regards,
Robert