INTRO2 replay warn logs with v3 onions

While testing vanguards 0.3.0 with tor 0.4.0.2-alpha and a v3 onion service that was only for my testing, I got several loglines to the effect of

Mar 07 11:10:17.000 [info] hs_circ_handle_introduce2(): We received an INTRODUCE2 cell with same REND_COOKIE field 1 seconds ago. Dropping cell.
Mar 08 12:05:58.000 [warn] Possible replay detected! An INTRODUCE2 cell with thesame ENCRYPTED section was seen 0 seconds ago. Dropping cell.
Mar 08 14:17:21.000 [warn] Possible replay detected! An INTRODUCE2 cell with thesame ENCRYPTED section was seen 59 seconds ago. Dropping cell.

The client was Tor version 0.3.5.7 (git-9beb085c), from Tor Browser 8.0.6. The client was accessing the service as follows:

while [ true ]; do
  torsocks wget  http://$MYV3_ONION_NAME.onion/404 -O /dev/null
  killall -HUP tor;
done

That v3 404 url is in fact non-existant -- it does just send back a HTTP 404.

I'll match up some log instances and attach.