Unknown Error Exception, Roto Brush/Drop Shadow Generated Generated an Error Exception

First, check if your video and composition have the same frame rate. If they don’t match, adjust the composition settings to fix it. Next, if Drop Shadow is causing issues, try pre-composing the layer. This means selecting the layer, pressing Ctrl+Shift+C (Windows) or Cmd+Shift+C (Mac), and applying Drop Shadow inside the new composition.

If the error still appears, reset After Effects settings. Close the program, go to ~/Library/Preferences/Adobe/After Effects/ on your Mac, and move the After Effects folder somewhere safe. Restart After Effects, and it will create new settings. Another possible issue is third-party plugins. Go to Applications/Adobe After Effects/Plug-ins, move any extra plugins to another folder, and restart the program to see if the error disappears.

Sorry to hear about the error, Callum.

This is a generic error that doesn't tell much about what's happening. Let's try to figure out.

Is this happening with a specific project? Corrupted media could be causing the issue. For testing, change the location of the media so that After Effects can't link it to the project. Check if that works. If it doesn't, try running After Effects in Safe Mode. See if the issue persists.

Let me know how it goes. Moving this thread from Bugs to Discussions for troubleshooting.