If a random number generator is working properly, then unlikely events
will occur - as was pointed out earlier, that's the nature of randomness.
Real dice don't have a memory - if I'm rolling two (fair, not biased) dice, and I roll 2 five times in a row, that's rare, but not impossible. But the important thing is that the next time I roll the dice, the probability of getting
another 2, is still 1 in 36 - the past sequence of 2s doesn't increase or decrease the probability of the next roll being 2. The same applies whether we're using two non-biased physical dice, or a non-biased electronic random number generator.
Strode's comment is relevant too. As humans, we're spectacularly bad at spotting and recognising randomness because
- Our brains are designed to find and recognise an immense variety of patterns, and they're so good at it that they can detect patterns even when no pattern is present.
- Our brains don't record memories like a video file on tape/disc that you can play back with fidelity. Our brains insert/invent details we didn't see at the time of making our memory, and the details can get altered with time and recall.
That's not something to be embarrassed about, it's a side-effect of the amazing brains we have as humans. But it does mean that when we are evaluating a random number generator, we have to rely on proper statistical analysis not perception, and not decide things from a sample too small to draw statistically significant conclusions, especially if it the sample was specifically chosen for analysis afterward it happened.
If you could predict "in the next Catan game I play, 4 won't be rolled all game" and then show this happened, then we'd have reason to doubt the quality of the random number generator.