RNG possibly not seeded sufficiently
The std::mt19937 generator is used in rng.cpp, but is only seeded with 32 bits. MT has over 2+ Kilobytes of state, and is slow compared to other generators. Maybe a different generator should be used, as the main advantage of MT is not being utilized here, or the seed should be mixed with some other fixed data in case of the majority of the internal state being zero initialized.