The analyzer detected a class definition or function body that occupies more than 2000 lines. This class or function does not necessarily contain errors yet the probability is very high. The larger a function is, the more probable it is to make an error and the more difficult it is to debug. The larger a class is, the more difficult it is to examine its interfaces.
This message is a good opportunity to find time for code refactoring at last. Yes, you always have to do something urgent but the larger you functions and classes are, the more time you will spend on supporting the old code and eliminating errors in it instead of writing a new functionality.