I've been trying to rack my brain as to why this isn't working, because it really should... In After Effects 6.5.1, a layer has a bunch of mask keyframes (shape). There was a problem with the underlying image not supplying enough real estate. So that the mask would actually show nothing in the area that it wasn't over the image. What I did was duplicate the layer. Changed the position/scale of the original, deleted the mask. Then went to the duplicate and copy/pasted the mask back. Naturally, the mask was no longer the way it was, but was now matching the new position/scale. So, there is a need to change those keyframes and make it go back to the way it was originally. I selected the mask shape, made sure all the keyframes were highlighted in the timeline. Went to the first keyframe, and simply scaled it down and positioned it to the way it needed to be. What's perplexing is that none of the keyframes followed suit, despite being all highlighted. The keyframes/vertex's were not changed...just the scale/position. I would've thought this would've made the change to all the highlighted keyframes in the mask. But it didn't. Any suggestions?
Right now, I'm in the process of basically redoing the keyframes individually. Hoping someone out there has an idea to shoot me.
It's been over a decade, so I hope you eventually found a solution to your problem.
If you haven't – and as a future reference for anyone who may come across your post looking for a solution like I did – here it is: