Sending new media without stopping previous raising the exception on media_player side.

home-assistant.log

2018-07-08 16:20:58 ERROR (MainThread) [homeassistant.core] Error executing service <ServiceCall media_player.play_media: media_content_id=http://192.168.1.201:8123/api/tts_proxy/add04a2695f53fdeb6217601c85af6c44abe2f38_en_-_google.mp3, media_content_type=music, entity_id=['media_player.philips']>
Traceback (most recent call last):
  File "/Users/yottatsa/Public/homeassistant/lib/python3.6/site-packages/homeassistant/core.py", line 1021, in _event_to_service_call
    await service_handler.func(service_call)
  File "/Users/yottatsa/Public/homeassistant/lib/python3.6/site-packages/homeassistant/components/media_player/__init__.py", line 441, in async_service_handler
    await getattr(player, method['method'])(**params)
  File "/Users/yottatsa/Public/homeassistant/lib/python3.6/site-packages/homeassistant/components/media_player/dlna_dmr.py", line 641, in async_play_media
    CurrentURIMetaData=meta_data)
  File "/Users/yottatsa/Public/homeassistant/lib/python3.6/site-packages/async_upnp_client/async_upnp_client.py", line 521, in async_call
    (status_code, response_body))
async_upnp_client.async_upnp_client.UpnpError: Error during async_call(), status: 500, body: <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<s:Body>
<s:Fault>
<faultcode>s:Client</faultcode>
<faultstring>UPnPError</faultstring>
<detail>
<UPnPError xmlns="urn:schemas-upnp-org:control-1-0">
<errorCode>705</errorCode>
<errorDescription>Transport locked</errorDescription>
</UPnPError>
</detail>
</s:Fault>
</s:Body>
</s:Envelope>