error from server log

alpha server running locally

> ERROR 2024-08-24 15:18:02,599 Catch unhandled error in CALL thread: null =>[CALL - 5] ThreadExecutorImpl$CachedThreadPoolWithException.afterExecute
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)
at java.util.ArrayList$Itr.next(ArrayList.java:859)
at mage.util.CardUtil.deepCopyList(CardUtil.java:1906)
at mage.util.CardUtil.deepCopyObject(CardUtil.java:1858)
at mage.abilities.TriggeredAbilities.(TriggeredAbilities.java:65)
at mage.abilities.TriggeredAbilities.copy(TriggeredAbilities.java:318)
at mage.game.GameState.(GameState.java:170)
at mage.game.GameState.copy(GameState.java:295)
at mage.game.GameImpl.(GameImpl.java:203)
at mage.game.TwoPlayerDuel.(TwoPlayerDuel.java:20)
at mage.game.TwoPlayerDuel.copy(TwoPlayerDuel.java:41)
at mage.game.TwoPlayerDuel.copy(TwoPlayerDuel.java:12)
at mage.server.game.GameSessionPlayer.prepareGameView(GameSessionPlayer.java:214)
at mage.server.game.GameSessionPlayer.getGameView(GameSessionPlayer.java:200)
at mage.server.game.GameSessionWatcher.lambda$update$0(GameSessionWatcher.java:54)
at java.util.Optional.ifPresent(Optional.java:159)
at mage.server.game.GameSessionWatcher.update(GameSessionWatcher.java:54)
at mage.server.game.GameController.updateGame(GameController.java:824)
at mage.server.game.GameController.lambda$init$3aa0d15c$1(GameController.java:124)
at mage.game.events.EventDispatcher.fireEvent(EventDispatcher.java:28)
at mage.game.events.TableEventSource.fireTableEvent(TableEventSource.java:44)
at mage.game.GameImpl.fireUpdatePlayersEvent(GameImpl.java:3158)
at mage.game.GameImpl.rollbackTurns(GameImpl.java:3965)
at mage.server.game.GameController.sendPlayerAction(GameController.java:540)
at mage.server.game.GameManagerImpl.sendPlayerAction(GameManagerImpl.java:127)
at mage.server.MageServerImpl.lambda$null$39(MageServerImpl.java:828)
at java.util.Optional.ifPresent(Optional.java:159)
at mage.server.MageServerImpl.lambda$sendPlayerAction$40(MageServerImpl.java:826)
at mage.server.MageServerImpl.lambda$execute$69(MageServerImpl.java:1161)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

Start with the stack trace in mage.util.CardUtil.deepCopyList at CardUtil.java:1906, then inspect TriggeredAbilities.java:65 and its copy method at line 318. Trace how GameState.copy and TwoPlayerDuel.copy are reached during GameSessionPlayer.prepareGameView and rollbackTurns. Done means identifying and resolving the concurrent modification, but the issue provides no reproduction or explicit verification test.

Written by the indexing model from the issue text.