buf in do_recv() in core.c is too small in case of TLS. TLS record size can be up to 16kB but buf is only 8kB. This leads to data not to be delivered at the end of a reply. At least not in a timely fashion, as it is eventually deliver when the connection is closed many seconds later. buf needs to be at least 16kB.
A commit references this bug:
Date: Sat Dec 7 11:39:36 UTC 2019
New revision: 519200
- Update to the latest GitHub commit: current version is from 2015
and is not compatible with modern OpenSSL implementations
- Set PORTVERSION to the version number as reported by `httperf -V'
- Increase buffer size in do_recv() to match TLS record size which
can be up to 16kB 
- When using TLS 1.1 or TLS 1.2, the first SSL_connect() may often
return error, while subsequent requests work fine -- to mitigate
this, try to SSL_connect() a little harder 
Approved by: maintainer timeout
PR: 230680 , 230681 
Should be fixed per ports r519200, thanks!