Rémi Bernon (@rbernon) commented about dlls/winegstreamer/media_sink.c:
TRACE("iface %p, stream_sink_id %#lx, media_type %p, stream_sink %p.\n", iface, stream_sink_id, media_type, stream_sink);
- EnterCriticalSection(&media_sink->cs);
- if (media_sink_get_stream_sink_by_id(media_sink, stream_sink_id)) return MF_E_STREAMSINK_EXISTS;
You'll need to leave the CS on the error path now.