Ok, sorry, so I checked and played around with your Capx and this is my feedback:
1) Your Sprite has Platform behavior and when using Arrow keys it behaves correctly (no jumping).
2) If using the D key as per your event the "jumping effect" occurs. I checked all collision lines and tried variations with other solid objects and in all cases the "jumping effect" happened.
My conclusion / advice to you:
I believe this effect happens because you are using the Move Forward action which "teleports" your Sprite 4 pixels into the solid object but since it cannot be inside a solid object there seems to be a push back effect which we see visually as "jumping effect".
To move your sprite you should not use such "teleportation" of X pixels, but you should simply say, if you do not wish to use Arrow Keys, on D key down SIMULATE CONTROL (under Platform) and choose Left if you want it to go left or right if you want it to go right, etc.