Game crashes when AI plays a card with cost {X} and that targets a player, this cards can be coded around that restriction and still work as per the rules.
The BIGGEST BUG the game has now is that crashes occur when a PERMANENT TARGETS A SPELL IN THE STACK, sometimes the AI can make this cards work (WTH!?) but never the player.
Effects like mirari and similar could be coded so that you don't target the spell but trigger and copy the source of the trigger, look at the code of mirari for this to be more clear.
This effect used to work for many many years I remember Glen Elendra Archmage being one of my favorite cards back in the day. This bug has been present since god knows when, as early as october 2016: https://wololo.net/forum/viewtopic.php?f=4&t=66296&start=150#p98160
Also freaking Lemures caused the AI to just keep repeating the effect so I put a limit on activations on them.
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