This happened to me before when I had a giant-sized After Effects project file. If the project file is small, it will open and save quickly. If the project file is large, it will open and save slowly. If it’s over 50 – 150 MB, depending on it stats of your computer, it may take forever to open and save. Even though it says that it’s 100% complete, it still may not be anywhere close to 100%. It could easily take over 10 minutes to open a project this large.
If you’re able to get the project to open, then try reducing the file size. You can do this by using compositions for repetitive footage, deleting unused files in the project panel, deleting unused footage in the timeline, removing unused effects, and deleting unused keyframes. You can always render and export footage with effects applied to them, import the rendered footage, and delete the footage with the effects.
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