Join me in the list for the same. I have had some serious problems with Dash Q-100 as well. Of course this was when I played offline, not on pro-pilot or EHM either, but just in general at home. An all perfect approach to the runway, as soon as I was established on the localizer, I thought I should do a manual landing instead of ILS approach hold. No sooner I released the autopilot, the plane started behaving very oddly and just went off control. I had to abort and close the flight. It was only with the Dash that I encountered that problem.
Regarding the nose wheel going down, FS I think does have some kind of a mechanism as to when a hard landing is done, the wheels does seem to "sink" into the ground, but that does not indicate a crash, as I have seen that on hard landing, my wheels go stuck but I don't get the message called crash. So I guess its all the same situation. What's causing this .. am not sure, but I think I can blame it on scenery too may be!!
Let try one thing, it this occurs again, lets post the following so that we can have some kind of tracking
1. Airport
2. Plane used
3. Landing speed kts and fpm