@Copterline 103. I disagree with much of your #505. The PF reporting heavy collective doesn't mean he needs more force than normal to move the collective, it's just his way of expression to describe the collective not remaining where he left it (because the collective force trim is no longer holding it in position).
Binding in the controls must be before the mixing unit if only one axis is affected, in this case only lateral control problem was reported. There is nothing I've seen here to indicate any binding in the collective, and nothing to indicate any hydraulic servo actuator problem.
I do not see anything to suggest the AP turning itself off (due to flight control binding or whatever). The FDR shows the AP turning off and then back on again within only a few seconds, which to me says the AP turning off was by pilot action (in all 9 instances). I would expect to see FDR data show the AP off for a much longer period before coming on again if it had turned itself off, because generally it takes pilots a while to notice that a single AP has dropped off.
The AP were never lost, the FDR shows they were on all the time (except when they were cycled off/on several times presumably by pilot diagnostic action).
Obviously something happened to spook the crew, my bet is an electrical gremlin of some sort got interpreted as a mechanical problem. A crew wouldn't ditch a helicopter for an electrical problem unless it was an electrical fire that couldn't be contained following emergency checklist action. The salt water bath all the electrical bits and pieces received wouldn't be helpful for replicating the problem, but the cause of a burning smell reported should leave some physical evidence in a loom or other component that an investigator could find.