As you already implied: when you’re not at home but travelling.

Usually a sign of multiprocessing/multithreading going wrong, e.g. accessing the same resource without proper locks like opening the same logfile in different processes and trying to write simultaneously. Those errors can be triggered just by reformating the code (or obfuscating in this case), thus changing the runtime behaviour slightly. Hard to find, especially since they’re dependent on the speed/workload of the machine running the code.

You are aware that the impossible sections were on purpose to sell hint books and to make money with the telephone hintline which one could call being stuck?