PIE: Warning: AttachTo: ‘/Game/Levels/UEDPIE_0_Level_0.Level_0:PersistentLevel.SprungWheel_BP_C_1.MassWheelConstraint’ root component cannot be attached to other components in the same actor. Aborting.
I have done everything(double checked it) in the last lecture and it’s complaining about this since the last lecture.
im having the same problem.
edit- try removing any AI Tanks and placing them again. it removed the error for me but im still getting NULL for some reason.
Edit- It was null because the spawn point component in the tank BP has its spawn class in the defaults reset because of a common bug in unreal. check that if you have the same problem.
I got this error too. It seems the hot reload doesn’t change the root component over to the constraint automatically in the blueprint when you change it in C++; you have to refresh it as it were.
I did this by reparenting the class to something else then parenting it back to SprungWheel.
Thank you dude. It worked 
I did the same thing few days back and guess what Unreal Magic Happened.
This seems to be a general problem if you change things in C++ and then want to have the changes reflected in the child blueprint class. Surely there’s a simpler way for doing this than changing the parent class to something else and back again?