Bisect and binary search. If the Module has been found that produces the error, I go to the fault-lines. These are: Data-Input and Filtering. States outside of the Set of accepted States (Anticipation-Error - the reason why every time you write else/default for anything else then a error- that's a error). Those points inside the code, where you switch between two brain language-models (arithmetic/data-handling) (procedural/object-orientated), (relational/ list-think), (value/state-handling) etc.

If you do that right, you can skip the reading and go right for the beef. Breakpoint.

Last but not least - good architecture, worst heisenbug wont cost you as much as the smallest architecture error.