C++ stragne behaviour with blueprint

Hello everyone! I’ve noticed a strange behaviour recently. First of all, UE4 tends to show fake errors after compilation. For example my code has no errors but compilation is failed and when I press compile several times again it becomes okay. Secondly, my BP class which was inherited from C++ super class got corrupted when I had changed the name of one field in C++. And Finally this. I have Health Component which was made in C++ and has default values in constructor. I put it on several objects and from time to time when I change component’s values in BP it affects all objects with this component and I don’t know why. I would really like to understand it.