Adobe after effects undo all my edit,why???

[Qzixas251320653tqt]

Hello, so i spend like few hours in roto bruash tool cutting frame by frame and after i check result its all gone, everything went to how it was... why? is there any way to prevent it???? i'm upset by this waste of time...

[Rick Gerard]

Rotobrush must be frozen to save the changes. If you did not freeze, it has to propagate again. Having to start over is not a bug. It is the way the tool was designed. 

If you spend more than a few minutes using Rotobrush, it is a very good idea to pre-compose the layer when Rotobrush has completed and then frozen, then go to the Composition menu and select Prerender. Follow the prompts to choose a location and then render the file. This will create a production-quality video with an alpha channel of your work. Rotobrush is a finicky resource-intensive tool that bloats the project file and can cause problems. Unless I can do the rotoscoping in about 5 minutes, I always, and I mean always, pre-render the layer and replace it in the composition. I then delete the Rotobrush comp completely.