Tobias Schlitt has provided a helpful hint for developers working with lots of objects, methods, and singleton patterned functionality to keep out of the same trouble he faced.
During my current exam phase I'm working on some tiny private project to relax after learning. In there I'm using a main controller class, which implements a singleton pattern and initializes several sub-controllers while being created. The singletons purpose is, that the other controllers can access to main controller and its functionality whenever they need, without storing a reference each.
The problem with the code (he gives snippets) was a recursive loop that was suddenly appearing. He finally tracked it down to a constructor in another class that was accessing the main controller's constructor. The issue was that the constructor was never finishing up, so a valid instance wasn't returned, so the whole thing started all over again.