I solved this problem re-setting unit and scale in Blender.
I made this animation using Blender and it seems like there is some compatibility issue between Blender and UE4.
As many other says, I set unit in Blender as Metric 0.01.
Because I animated my character in different unit, I should scale it up x100 and apply that scale.
This made me loose some part of animation(I should do this again).
But in UE4 Sequencer, scale change problem is no longer exist anymore.
Is there anyone knowing use Sequencer with scaled up skeletal mesh?
yeah blender and unreal have always had that problem. for the root motion settings, instead of ref pose try the other options i have a feeling that might fix it.