Expendability

This move would reap the account below the existential deposit; leave dust or explicitly transfer-all

The transfer or payment would drop the sender below the existential deposit and kill the account while keep-alive semantics are required. Compare the sender's free balance minus the amount and fees against ExistentialDeposit, or use transfer_allow_death if reaping is acceptable.

Declared by the Balances pallet; it classifies to the semantic code insufficient_balance.

Remediation

This move would reap the account below the existential deposit; leave dust or explicitly transfer-all

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