OMD2 - Weird 14x Combos on Double Decker (3)

Continuing the investigation about the odd 14x combos observed.
This time, upon Rogotin's suggestion, I've simplified the setup to try and make it easier to understand. I'm using Push Trap (longer range, no stun), Tar (persists), Steam Trap (faster reset, no chill), Grinder (faster unjam, no bleed), and Winbelt. The crossbow is only used against the heavies at end of the waves, it's not shot at the mobs.
So Tar + Push Trap + Grinder + Steam Trap + Windbelt : max combos observed should be 5x.

Well, I did get a bunch of 6x...

Discussion here : http://www.robotentertainment.com/forum/topic/Unexplained-14x-combos-Double-Decker