Throttle levers question

Hi, I came across a very weird explanation of facts of a plane crash. An official report stated more or less something like this - "The throttle levers retracted after being set to START - which may prove nobody controlled their position. The levers' locking mechanism was not engaged due to the previously enabled Automatic Thrust Control."

The plane was a Russian made Tu154. The auto-throttle was on, the pilot supposedly pushed the levers all the way to start level which took approximately 1 second and the movement disengaged the auto-throttle.
Then the levers gradually dropped back to where they started which took maybe another 4 seconds or so.
The report implies the pilots did not control the throttle and that the throttles fell back under their own weight.
So my question is basically - is it even remotely possible?