(SPOILER) Old Jonas and old Martha...
... shouldn't exist the exact moment Jonas and Martha thwarted the car accident without they could even realising it.
Instead, they were shown turned into sparks very slowly while embracing each other.
Doesn't make any sense considering what they erased from existence / prevented from happening are the whole worlds entirely, not just the humans. Yet only humans disappears.
But then photos on the bunker walls were turned into sparks as well, nothing else. Which is just random.