I ran into an issue that seemed like a bug when trying to store an instance of a class in Memory. Here's some minimal code to reproduce it:

main.js:

class Doggo {
  bark() {console.log('woof')}
}

module.exports.loop = function () {
  if (Game.time % 5 == 0) {
    Memory.pooch = new Doggo();
    console.log("Single pooch instanceof Doggo (same tick as created): " + (Memory.pooch instanceof Doggo));
    Memory.pooch.bark();
  }
  else {
    console.log("Single pooch instanceof Doggo: " + (Memory.pooch instanceof Doggo));
    Memory.pooch.bark();
  }

}

And sample output: