Warning: Padding negotiated cell from wrong hop on circuit

Running chutney's single-onion-v23 network, I see the following warnings:

Warning: Padding negotiated cell from wrong hop on circuit
Warning: Received circuit padding stop command for unknown machine

These chutney networks are running 0.4.4.0-alpha-dev (f231827946).

These warnings appear to be timing-dependent, they don't happen all the time.