Playback for editing OK but exported video is stuttering

Hello,

I have multiple timelines and a timeline regrouping all the timelines.
When I edit my projet, the timeline is playing fine. Image and sound are synced.

When I'm in "render" workspace and I playback basic timelines everything is fine.
When I play or export the timeline containing the other timelines I have stuttering during playback.

When I export timelines one by one they are all fine.


Any ideas why it's stuttering when exporting a timeline containing multiple timelines ?

Thanks