Unreachable

announce_next_key could not identify the current block author via the FindAuthors lookup, which should be impossible in a normally authored block. Check the block's author digest and the shield pallet's authorship wiring.

Declared by the MevShield pallet; it classifies to the semantic code internal.

Remediation

A chain-side invariant failed; nothing to fix client-side — report it if it persists

The same explanation is available in the terminal: btcli explain Unreachable.