I've never done a platformer, but I do see all your animations are set to 'play from beginning' every tick. (they start over many times a second.)
If there is a little green arrow like in the event next to the keyboard icon, then it is a trigger, and fires when the key is pressed.
If that spot is blank, then it actually runs Every Tick.
So if your PlayerBox is moving, it will always be on the first frame of 'Walk'
If the character is moving and falling, it will show the first frame of falling, because it changes to 'Falling (play from beginning)' just after changing to 'walk' animation.
You could try adding 'Trigger once while true' to each, so that it only fires once when ever the event becomes true again.
Does that offer a lead to the problem?