void rampart
I barely know how to explain this well, but when an enemy dies in the same row as another and you have two units triggering eachother, normally there would be logic to prevent the two going infinite.
However with a second unit in row, the game lets it happen since there's multiple different enemies and so who you're triggering off gets a bit lost in the system.
but that effect then prolongs after the other units in row die and you're left with one, so you end up causing an infinite that shreds through whatever unit is left.
I think this explanation sucks, so I'm going to add 3 videos demonstrating it (2 from @/SuSu609, and 1 I recorded to demonstrate it. Susu609's are rather quick though so it's harder to understand what's going on.)
umbral ferry