same issue  

not a pro player but notice that the trim keeping rolling down (nose down)

all the GA got the same issue but not commercial plane   even sometime the AP is ON the trim will keep rolling down

got few times even occurs while taking off  accelerating and sudden nose down on the runway

If your trim is changing by itself, check your autopilot. You may have it on and have the altitude hold set. First try turning the autopilot off and see if that clears it up.

sure not the AP problem   becoz this will happen even in trainning mode (tutorial)  step by step as well

Just registered to say that I'm having the same problem. Never noticed it in FSX. I've been flying the DA40 and 62 but the trim seems way too eager.  Just a couple of presses and the plane will over pitch. I'll hold the stick level, select the pitch with a couple of presses but instead of allowing me to release and maintain the attitude, the nose just goes way past what the few click inputs should sensibly dictate.

Also I've noticed that during the autopilot bug, if I go to the chase cam, the pitch is set at 100%, so I think there is deffo an issue. I'm not a real pilot but I've never had this issue in any other flight sims.

I have noticed that you need to make very small changes to the trim on the c172 otherwise it's all over the place, but I am using the saitek trim wheel

If you use Honeycomb Alpha Yoke (or any yoke/joystick/throttle) with 2 (or more) position switches (which send signal no only on press but continously) you trim inputs will be multiplied 10x making the plane barely controllable. In such case you have to remove all the assignments fro 2 (or more) position switches. The same bug applies to setting heading bug (10 degree increments instead of one) which is easier to spot than the exaggerated movement of the trim wheel.

The planes/controls are definitely super twitchy.  I'm flying smaller GA planes and they are far, far too hard to fly.  A 172 shouldn't handle like a fighter plane.  I've turned the sensitivities way down on all my controls and still things are too twitchy.  I was just flying in the DA62 and my climb rate bounced between negative and 2200.  I'm afraid to let go of the controls to turn on the AP.  

I'm not a real pilot, but I've flown the REP 172 in Xplane and that plane is simple to trim and easy to hand fly.  In FS2020, I'm looking to turn on the AP immediately because everything just isn't fun to hand fly.  

Hoping they can address this, or at least 3rd party devs can figure it out. 

Squirrel has some very good tutorials on this subject on his YouTube channel. I have setup two profiles in control settings. One for stick controlled aircraft (Saitek X52) and another for Yoke controlled ones (Honeycomb Yoke). Each Control unit then has two profiles. One I call Null and the other either Stick or Yoke. When flying a yoke aircraft the Saitek becomes Null and visa versa. Squrrel describes this far better than me.

 i dont see anyhting wrong with the trim, controls are too sensitive yes.

but i can fly level and trimmed, with  ga aircraft

Trim runaway is real world issue scary stuff , I just googled and read a bit on the subject really had no idea the history , accidents and real world procedures till now.

I was just about to post a message about this problem and then stumbled  on this thread ... 

There is most definitely a problem with the GA Aircraft in FS2020 .... they are impossible to fly !! 

I have been simming for over 30 years and never experienced such bad flight dynamics!! 

Lets hope they get this sorted soon! 

Hello ! i have exactly the same problem !!

It's impossible to fly with Auto Pilot in thoses condition ...

Do you know how can i report the problem ? ( i'm sur they know it, but one more report can't be bad )