Rotoscope mask acting erratic in main composition

[BenJH]

Hi.  I'm very new to After Effects so I am not sure if I have done something wrong here.  I have rotoscoped some stock footage that I want to incorporate into a project.  I have created a precomp of the rotoscoped footage.  Within the precomposition the rotoscope works perfectly.  When I add the precomp to my main composition the mask begins to change and collapse in on itself.  When I double click back into the precomposition it is fine, no problems.  I thought it might be an error so I purged the memory and cache.  That seemed to fix the problem once, but as I made some more changes the problem came back.  I have purged again, but this time it has not solved the problem.  Is this an error with the preview or is my mask actually changing?  Anything I can do to fix this?

Thanks for the help!

[Ko.Maruyama]

If your precomped footage of the rotoscoped material isn't the same frame rate (or a stretched frame rate) in the main comp, the collapsed function may be changing when those roto keyframes land.

In the Preomp's Composition Settings, make sure to check "preserve frame rate" - that may solve the issue.

[OussK]

As KoMaruyama Say's, you should have the same frame rate for all your compositions 

[Rick Gerard · Accepted solution]

If the rotobrush has not been frozen you are going to have issues. 

Any time I use Rotobrush on a layer that is more than a couple of seconds long I pre-compose that layer moving all attributes to the new comp and opening the new comp. Now I have a separate composition that only contains one layer with Rotobrush applied and frozen. I then use the Composition menu to Pre-render that Rotobrushed layer and end up with a "lossless with alpha" copy of the footage that automatically replaces the nested comp in the project. I then delete the pre-comp, reduce the size and complexity of my project, add stability to the project, and reduce the final render time. 

I hope this helps. 

One more thing. When sharing images please use the Toolbar or drag them to the reply area and expand them. "The Drag &d drop here..." area is buggy and difficult to use for images.

[BenJH]

Thank you!   That did it!