If the board has no matches after the enemy team goes, it reshuffles on their turn. This reshuffle can produce matches which then reward them with AP.
I think this is the same thing that is mentioned on the Bug Megathread
Board shuffle causes damage
When no matches are left, the board shuffles. It should not match anything and cause damage.
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I’ll edit the description to include your “reward them with AP.” part.
It also rewards the enemy team damage and AP whether it’s their reshuffle or yours.