I managed to solve the problem. It seems that this problem only occurs when using TLS 1.0 which was the highest allowed by the backend servers by default. Enabling TLS 1.2 on the servers and telling squid to use this fixed the issue.
Hopefully this will help someone else experiencing the same issue! -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Squid-3-3-4-Zero-Sized-Reply-for-HTTP-POST-tp4665601p4665664.html Sent from the Squid - Users mailing list archive at Nabble.com.
