I haven't got two minutes to watch the video, but would suggest that it is sheer coincidence, possibly due to a wind gust. Have you observed this over many flights, or just the one?
The elevators float freely, but there is a disconnect between control columns in case of a jam somewhere in the circuit. The FCOM cautions about doing flight control checks in strong tailwinds, because it is possible that the controls will disconnect. They can be reset from the cockpit if this happens.
One for an engineer to answer more completely.
Last edited by Mach E Avelli; 23rd May 2015 at 04:13.