C - Crush Wyvern
Level 4 LIGHT Machine-type/Union/Effect
Once per turn, you can either: Target 1 LIGHT Machine-Type monster you control; equip this card to that target, OR: Unequip this card and Special Summon it. A monster equipped with this card is unaffected by your opponent's Trap effects, also if the equipped monster would be destroyed by battle or card effect, destroy this card instead. If this card is sent from the field to the Graveyard: Activate this effect; you can Special Summon 1 Union monster from your hand.
This is an anti-cheat erratum focusing on the possibility of C - Crush and either A - Assault or B - Buster being sent from the field to the graveyard simultaneously. Pre-errata, one could activate C's effect as chain link 1, and A or B's effect as chain link 2, and resolve backwards, adding a Union to hand and Special Summoning that same Union. This is all legal play as long as you had a Union in hand when you activated C's effect.
The problem lies in confirming that that was the case. In the real world, you have to call over a judge every time this happens to confirm that they had a Union in hand, which is a nuisance. So, inspired by Gilasaurus' recent erratum, I made the effect compulsory so that it will always trigger, but the actual summon optional so that you don't give your opponent lots of free information should you not have a Union in hand.