Quicktime Player recording with Applescript broken on Mavericks?

I have this simple code:

tell application “QuickTime Player”
activate
new screen recording
document “Screen Recording” start
delay 10
document “Screen Recording” stop
end tell

This records a 10-second movie on my 10.8 machine with no problem. But on 10.9 mac-mini, QT hangs at the stop action above. It hangs at the window with message “Finishing Recording”. I have to force quit it and still same thing. If I do these steps manually, they work. But with AppleScript or even same steps with Automator have same issue.

I upgraded to 10.9.2, but still same issue.

Is this a known bug? Any suggestions for a work around?

Thanks.