I've checked an example and it looks to complex for me. So there is no possibility if 2 sprites one on another to define which object was clicked? So why does Event for mouse has a name "On object click" if in real it clicks everything what under this point and it can be 100 objects? May be it is good to change the name or description for this event?
I think you need to understand the difference between object types and instances as well as how events work.
When you click an object type it will pick the instance(s) you are clicking on.
If two (or more) instances are in the same spot you are clicking on, all those instances will be picked by the event and the actions will be applied to those instances.
Unless you do use further conditions in the event to thin out the instances picked (what "Picking top instance" does returning only a single instance).
or may be you can send me your event tab (as photo) i will try to reproduce it on my Mac.
I already did provide you the content of the project as text in my previous message.
To add an image, upload it at the bottom of the edit box, it gives you an ID.
(where ID is the actual provided number) to your message for the image to display.
R111 is the latest stable release available at the time of writing this message.