Pretty much impossible to assist without seeing what you've done with events.
Okay here is what I have
+ Keyboard: On Z pressed
-> Sprite3: Spawn Sprite6 on layer -1 (image point 1)
----+ Sprite3: Is mirrored
-----> Sprite6: Set angle to 180 degrees
+ Keyboard: On A released
-> Sprite3: Stop animation
-> Sprite3: Set animation frame to 0
+ Keyboard: On D released
-> Sprite3: Stop animation
-> Sprite3: Set animation frame to 0
+ Keyboard: On A pressed
-> Sprite3: Simulate Platform pressing Left
-> Sprite3: Set animation to "LeftWalking" (play from beginning)
-> Sprite3: Start animation from beginning
-> Sprite3: Set Mirrored
+ Keyboard: On D pressed
-> Sprite3: Simulate Platform pressing Right
-> Sprite3: Set animation to "RightWalking" (play from beginning)
-> Sprite3: Start animation from beginning
-> Sprite3: Set Not mirrored