in general the bot seems to not like rng very much. Very often cards like arcane missiles are not played, if the enemy has minion/s with 1 life because the bot doesn´t assume that the missiles will have some value very likely. And cards like crackle are used as if they would cause the least amount of damage possible.
And as the unstable portal can be every minion there is no clear value set for this card. General I think unstable is (except for arena) is not that good. Just take it out of any construced deck and the bot won´t have an problem with it.
