MouseEvents for instantiated prefab not called

Hello,

after some hours of research i will finally post here
My problem is that I am not able to receive any MouseEvents on newly instantiated prefabs unless i modify them in any way in the unity editor while the game is running. I've already checked possible issues with UI but I can exclude that.

Prefab looks like that:


Script on the Prefab (EntityHandler deriving from MonoBehaviour):



Is there anything the internet didnt tell me yet or am I just blind?
Any suggestions appreciated