upforwd test causes assertion failure in streamdns.c

I modified the upforwd test to add a delay:

--- bin/tests/system/upforwd/tests.sh
+++ bin/tests/system/upforwd/tests.sh
@@ -23,6 +23,8 @@ RNDCCMD="$RNDC -p ${CONTROLPORT} -c ../common/rndc.conf"
 status=0
 n=1
 capture_dnstap() {
+       echo_i "sleeping 15 seconds"
+       sleep 15
        retry_quiet 20 test -f ns3/dnstap.out && mv ns3/dnstap.out dnstap.out.$n
        $RNDCCMD -s 10.53.0.3 dnstap -reopen
 }

With this change, I get the following failure fairly repeatably:

12-May-2023 18:59:21.745 dispatch 0x7b5000050000: TCP read:timed out:requests 20
12-May-2023 18:59:21.745 dispatch 0x7b5000050000: TCP response 0x7b5000050200: reading from 0x7b4c00040180
12-May-2023 18:59:21.745 netmgr/streamdns.c:834: REQUIRE(sock->recv_handle == ((void *)0)) failed

The failures also happen with revision 88cf7e7e (main yesterday before RCU changes), when compiled with thread sanitizer and without.

I am running BIND on my Debian Bullseye box.