I remember reading somewhere in the rules that if a unit in a stack is KO or BU then the rest of the units in the stack are suppressed. I can't find this now. Can anyone give me a reference?
220.127.116.11 AP Damage & Effects -> BU Brew-Up.
"When a vehicle suffers a brew up result, all friendly ground units
in the same hex are immediately Suppressed. It does not apply
to passengers under cover (see 18.104.22.168.3)."
Also, KO does not causes it. Only BU.