It should be an easy fix. Just make it so that such events are timed. Make the first conversation impossible to access after say 2-3 long rests after its initial trigger point. Once the first one in sequence locks, the second one unlocks for X-Y long rests. That way, we can avoid sequence breaks.
Another alternative is to do what DoS2 did, if you fail to do a critical quest. You failed that play through and won’t get to see any of the char quests. Or do what kingmaker did, and have certain events tied to a game over screen. Eg: gale dying and waiting 7 days [not sure if that was confirmed to be fake or is real].
