I've just started using v21.08.1. I was working on an old project. Then I wanted to change the project properties (screen size). It crashes every time. Since I've just done that with two other projects on v21.04.2 I decided to go back. But then I found out project created with v21.08.1 can't be opened by my old Kdenlive:

I'm wondering why such big change in a minor release? Such situation always stops me to upgrade because if I hit on a bug I have no chance to go back

Usually kdenlive saves a backup file when you open an old file with a new version. But, yes, you can't open a newer version file with an older version, that's the case everytime.

It is actually recommended to not change versions when working on a project.

Arkengheist wrote:But, yes, you can't open a newer version file with an older version, that's the case everytime.

If that's the case I must have been very lucky all the time . I haven't encountered that problem until now (except switching between mayor releases).
I always keep several versions of Kdenlive to ensure I can re-use older projects with old features.

I've just created a simple project with v21.04.2 and re-opened it in v20.12.3 seamlessly (without any warning). When I did the project in v21.08.1 and re-opened it in v20.12.3 I got the above error. Conclusion, I'll stay with v21.04.2 and avoid the new "feature" of v21.08.1.