I still got the same issue in the latest stable build.. not exactly like this, but load bumping around left, right, up and down suddenly.
this happened while flying as slow as 20kph. Same with flying fast. At some point the load(a retextured Hunter/M-ATV) flung forwards and backwards, getting me up to -30kph, ending in a helicrash with load in heli or in water at some point.
Edit: I am flying without AFM. Happens with AFM as well though, as a friend has the same issue with AFM.