Too Long TCP Handshake / Too Many TCP Retransmission

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Hello,

We have a webserver for API and a game client. We process API requests from the game client but sometimes it takes way too long for a request to come back. Sometimes we have problems with latency, sometimes timeout or sometimes weird Unknown Errors. I currently have a wireshark capture;

First part of the capture

Second part of the capture

By the way; we don't have such problems when Connection: http-keep-alive is open. I believe we are having issues with the TCP Handshakes.