Trouble with objects vs instances?

I've set up some events that work perfectly if there is only one instance of an object. But once I add a second instance, it just doesn't work. I'm sure it's just my ignorance, but I don't understand how to differentiate instances when making events.

Example, I set up object A to be destroyed when object B has a collision with object C. Works perfectly. But when I add another instance of objects A and C, I've had either all of the instances of that object get destroyed or sometimes neither instance gets destroyed. How do I differentiate which instances are affected? I assumed UID but I don't see how to choose that under events.

Also, is there a way to group two object instances together? Say I have an object but want a second collision box for it (so that another event is triggered separate from the second collision box). I make an invisible collision box and place it. It works. But if I copy both instances, the second set of objects don't behave like I expect.

Thanks so much for all of your help.

It takes a while to get used to picking instances in Construct. When you say destroy object A, it's not related to the B and C that are overlapping. I can't see the game so I don't know how they should be related but if it's a switch of some kind you can use instance variables on the instances and pick that way to match them.

That was my question. When creating events, how do you differentiate between instances? I'm sure I'm missing something small but I'm stuck. Thanks for your reply.

Thanks again. I found a workaround that was pretty simple. I instead used one of the objects, different but consistent in every case to be the condition. There's surely a more elegant way than what I did, but it's a solution. I appreciate the info though.