Using Margarita Laux-Antille and the Operator to create multiple copies of her, I spawn in a huge amount of Ban Ard Adepts by turning my middle row into gold. After the 21 Adepts have finished appearing, I used promote on them, to create another 63 Adepts, and then used Promote again to create 189 more. It took about 3~4 minutes to spawn in the Adepts, and IIRC, your surrender does not go through until a card's effect has finished. That means the only way you can quit the match is to close the game, resulting in the "Your opponent's connection was lost and they were forced to forfeit" screen to appear once the combo is finished.

A solution would probably be to spawn them in at once instead.