Inability to respond to lethal damage
My opponent attacked, and after blocks I would be taking lethal damage and the system appeared to go into the auto-finish mode where you can not concede with lethal damage eminent. Issue being that I was holding a Savor in hand with four open mana to both kill a 3/2 and then gain the three life from the food token leaving me at one life.
This cost me the game.
Additionally, this is not the first game ending bug I have reported, with no feedback, and no reconciliation? Is that not a thing on Arena?

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DAC169#34537 commented
There are several cards your opponent could have that would make you either unable to cast spells & use abilities on their turn or only able to cast spells at sorcery timing. Did they have any of those out?