Steady Growth and Sacrificial Hymn may upgrade the same boon.

[ACCFCECD]

For example, when Steady Growth upgrades your epic boon into Heroic boon, Sacrificial Hymn will still attempt to replace the epic boon with heroic boon, even though there is no corresponding Epic boon left now.

[TheSwanDragon]

Heyo! Thanks for the report - could you also report that in-game with f10? It's fine to do so after the fact.