I did find a workaround by advancing the music video audio by 24 frames. But it did not matter. Even the beta 18.01 still had the out of sync audio on the rendered mp4. I even tried rendering to the new webm format same deal audio out of sync. I am working with green screen and using composite transition and chromakey effects. That all works great! Audio is a separate music track so if I add in another audio tack advance it 24 frames ,mute the edit sync audio it works! This is a new issue to me with kdenlive. Beautiful rendered file from beta 18.01 set with highest quality huge file 1.3 gb for tge 3 minute music video. I could post a link.

I have the same issue using a video file from a security camera with sound. The video file is broken down in parts of 20 minutes for which I use kdenlive to glue these together to one file. The resulting mp4 file shows the out-of-sync audio. My current solution is to split off the sound using ffmpeg, delay it one second (25 frames/sec) using sox and merge the video part and new sound file using ffmpeg.