TLS record lost -- AapacheBenchmark-session is not closed

[ymarkman]

Using NGINX-1.21.6 as TLS test-server  with remote Apache-Benchmark(AB)
test-client
Both Server and Client are on Ubuntu20.04
For >6 workers on NGINX and >16 concurrent sessions AB sessions (ab -n400
-c32 https://)
a couple of test-sessions are not closed and AB reports timeout for them.
TCPDUMP analizys discover the a TLS-Record is lost == Not Sent by NGINX (or
NET-stack) towatd OpenSSL and out to NET-dev.

Anybody have seen same/similar?
Thanks

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,295740,295740#msg-295740