How do I troubleshoot quirky score/lives issue?

I have a simple game: 3 different sprites are spawned and travel off the screen in different directions. Clicking (or touching) the sprite will add 10 points to the global variable "score," while the sprite going "outside layout" will subtract one life from the global variable "lives."

I'm finding as I test-play the game that both global variables will change value in a way that doesn't reflect what is happening on the screen. For example, 2 sprites may travel off the screen at the same time, but "lives" only gets reduced once. Or I might have scored 50 points from clicking on 5 sprites but my successful click on a 6th sprite takes the score back to 30. I'm not sure how either one of these scenarios is even possible when the events and actions are set properly. Or am I missing something?

(I was hoping to add a picture of my event sheet, but am a newbie and don't see how to do that)

To get help for troubleshooting, people will commonly upload their project as a .capx to a file host like dropbox.

It will be difficult to help you with your problem with that description alone, but if we can see the event sheet it will be much clearer.

Post the .capx somewhere or an image of your events and then paste the link here but put spaces in it... h t t p : \ etc till it works.