Warning: RELAY_COMMAND_INTRODUCE_ACK on padding circuit

When I run the new mixed+hs-v23-ipv6 chutney network from #33333 (moved), I see the following warning:

Ignored cell (40) that arrived in padding circuit 32.

I am running Tor 3.5.8 and 0.4.4.0-alpha (a6509cb867).

This issue appears to be timing-dependent: I saw it on one run, but I did not see it on the next one.