Problem with Automator/AppleScript Question
I suspect you may be getting this error because you are trashing folders and files in the same action. In other words, if automator tossed out a folder containing a '.mov' file, it will toss out the '.mov' file as well; then (later) when automator tries to toss that '.mov' file, it cannot find it, because it's already in the trash.

First solution to try: move the kind is folder option to the bottom of the list, in the hopes it sorts folders last. 

If that doesn't work, then you may need to complexify your workflow with a variable, like so: