Event are ok.
Almost definitely the problem is with the origin image point or collision polygons in "Idle" animation.
If origin point in one of the frames is a bit lower, this makes the character to lose contact with the floor and it triggers the "Platform On fall" event.
Use a single invisible rectangular sprite with platform behavior to control your character. And pin your existing sprite with all animations to it.
So i would code the rectangle to move and jump and stuff?