Problems muxing video (example doesn't work)

[MaxRev-Dev]

I have problems with muxing video from example.

I tried MacOS and Devian systems with packages from pip - 14.1.0 and 13.1.0 (pip install av or pip install av==13.1.0). No modifications to packages, fresh venv installation.
My environments are Sequoia 15.2 and a Debian 11 container.

In output I always have a file with empty frames.
I tried original MKV example and the modification below. It's always gives 4kB file in the end.

ffprobe output says it's empty, so no data muxed.

[h264 @ 0x144110010] no frame!
[h264 @ 0x144110010] missing picture in access unit with size 1

My code sample:

import av
import av.datasets

av.logging.set_level(av.logging.VERBOSE)

input_ = av.open(av.datasets.curated("pexels/time-lapse-video-of-night-sky-857195.mp4"))
output = av.open("remuxed.mp4", "w")

# Make an output stream using the input as a template. This copies the stream
# setup from one to the other.
in_stream = input_.streams.video[0]
out_stream = output.add_stream('h264')

for packet in input_.demux(in_stream):
    print(packet)

    # We need to skip the "flushing" packets that `demux` generates.
    if packet.dts is None:
        continue

    # We need to assign the packet to the new stream.
    packet.stream = out_stream

    output.mux(packet)

input_.close()
output.close()

[WyattBlue]

pull requests are welcome

[MaxRev-Dev]

@WyattBlue sorry, I have no idea how it works. I'm willing to help, but that completely out of my scope.
I tried Win/Debian/MacOS and there's no difference. Is there any workaround? Should the example listed in the docs work from the box?