Does anyone know the cause of action from here?
Set the clicks on the dampers.
The standard settings offers way to little damping and riding get flimsy imho. I have the KTM 450EXC -14 which is pretty much identical minus the forks, I am the same weight as you.
I set the clicks to:
Rear:
comp 15 out
rebound: 7 out
Fork:
comp 15 out
rebound 10 out
Suits my riding fine and just meant as an idea that you may try