Replays not always showing up

Out of the past 5 games, three have shown up in the replay system. They do not hold for 40 days, and sometimes just poof out of existence. Of course they always seem to happen when I see something suspect.

Something isn't going right, and I'm not the only person with this issue. It seems to be the case that if I don't have it, others in the same game don't have it.

I think each update wipes replays, but also, the game doesn't record each replay, from what I can tell. Some matches I've never even seen show up to begin with.

I've had matches I've never played in show up before, then poof out of existence minutes later.