For what it’s worth, the Run-time problem error messages for abandoning an activity and ending an activity seem to be flipped, so that’s probably supposed to be a message that tells you you’re ending an activity that isn’t going on. Which is hardly less mysterious.
This makes it seem like it’s parsing the command and coming up with nothing because everything is excluded from TAKE ALL; then, since figuring out whether the player’s command includes “[the barrel]” requires running the parsing routine again (I think), it has to run the deciding whether all includes rules again while printing the parser error. And here, somehow, the deciding whether all includes activity maybe isn’t getting started properly, so when Inform hits the “it does not” in the “exclude scenery from take all” it thinks that the activity is being ended without having been started? I don’t know what’s going on in the internals at all.