Hi everyone,
Actually I work on a very very big project. It's not finished yet but I try to do some render to send to the man who ask me to make this video.
First, it's in 4K 60fps and that take a very very long time to render 30min of video (3 or 4h). I have an i9 9900k + 48go of ram so hardware is good...
The other problem, more important, if I render the whole movie, audio is out of sync. That's progressive and more I progress on the movie, more is out of sync. I haven't this problem during I work on the project in Kdenlive (18.12.1).
If I render just a little bit of the movie, it's ok too.
I saw few things about this problem on internet but I can't find a solution and all posts are old.
Do you have any idea ?

This morning I make few rendering test by deleting audio tracks one by one. Now I have just video tracks and same problem....
Videos are in 4K 59.94 fps from a gopro.
I don't understand why audio is out of sync after rendering...

We have rendering sync problems but not really understood why. Especially in long videos (>20min) with lots of short clips.

GoPro 7 black has 4K 60fps. Why do you have 59.94fps?

As far as I see GoPro has not uneven fps frame rates.

With the last test you made you have a video and audio track only. Correct? To which format do you render? MP4 or MP4-H265?