Magmatic Channeler doesn't allow you to play MDFCs

[bobwoco]

When a card with an alternate cost is exiled with [[magmatic channeler]], you cannot cast it for that cost. This was observed two seperate times, once with [[bala ged recovery]] not being able to be cast on its spell side and once with [[vault skirge]] being unable to pay life.

[github-actions[bot]]

Magmatic Channeler - (Gatherer) (Scryfall) (EDHREC)

{1}{R} Creature — Human Wizard 1/3 As long as there are four or more instant and/or sorcery cards in your graveyard, Magmatic Channeler gets +3/+1. {T}, Discard a card: Exile the top two cards of your library, then choose one of them. You may play that card this turn.

Bala Ged Recovery // Bala Ged Sanctuary - (Gatherer) (Scryfall) (EDHREC)

{2}{G} Sorcery Return target card from your graveyard to your hand. :arrows_counterclockwise: Land Bala Ged Sanctuary enters the battlefield tapped. {T}: Add {G}.

Vault Skirge - (Gatherer) (Scryfall) (EDHREC)

{1}{B/P} Artifact Creature — Phyrexian Imp 1/1 ({B/P} can be paid with either {B} or 2 life.) Flying Lifelink (Damage dealt by this creature also causes you to gain that much life.)

[xenohedron]

Note that neither scenario is actually an alternative cost:

• MDFC is a separate castable component of the card- this is a common bug not handled correctly.
• Phyrexian mana is handled separately as a way to pay the Phyrexian mana cost and I'm surprised this could go wrong.

[xenohedron]

Can't reproduce the second- Phyrexian mana works fine for me. Won't let me play either side of Bala Ged Recovery, so I suspect it just doesn't handle MDFC correctly.