Opponent calls my coin at start of their turn

[tracer]

Game #170380 on oregon

At the end of my turn 11, I have two Coin of the Realms on my tavern mat and my opponent has none.
At the start of my opponent's turn 11, they were given the option to call a Coin of the Realm. Doing so did nothing for me or them (despite the display of 3 actions in the screenshot), but did take the Coin off of the mat and it displayed in the play area at the start of my following turn.

We did an undo back to before that point - my opponent did not have the same option the following turn.