Twice this has happened to me.

A version of the game state is: Agatha's Soul Couldron in play, Vivi in play, all my lands tapped, and no other creatures in play. No one-cost spells available, but yes a 2 mana spell available.

The bug is: I tap the soul-couldron to exile a vivi from my graveyard, putting a +1/+1 on my in-play Vivi. I intend to use both the Vivi mana ability, and the couldron-granted mana ability to generate 2 total mana to cast my 2-mana spell. Instead, the game auto-passes the rest of my turn as if I can't play something!

The behaviour should be to not pass the turn, and instead let me cast my 2-mana spell, by actually counting BOTH vivi mana abilities when checking the total mana I could produce!