I'm coding an API for Playfab using Game Maker Studio.
Everything worked just fine until one day when the first http request of the API started to take ~30 seconds. I started debugging the API and downloaded Fiddler 4. When I check the "Decrypt HTTPS traffic" option in Tools > Options > HTTPS everything starts to work just fine and the first HTTP request takes 0.7 sec intead of 30. After the first HTTP request everything works correctly whether I am using Fiddler or not.
Weirdly, every else HTTP (and HTTPS) request works fine when using different backends (calling them using exactly the same code as my API).
Also the Playfab API I'm writing works just fine on my other PCs (but I don't know how rare problem this would be if I would publish my API). Also the http request has no problems when using Postman.
I read the "Help! Running Fiddler Fixes My App???" article you wrote. I have the "Connection: Keep-Alive" in my headers, I'm using HTTP/1.1, I'm not using any proxy expect the one Fiddler provides.
This is the code I've isolated the problem to. I'm using GML (which GameMaker Scripting language, but should be pretty easy to understand).
The engine is not open source so I can't see what is happening behing the http_request(), but as I said this code works fine on other computers and every other http_request with different domain works just fine, so that shouldn't be a problem. But otherwise I'm pretty helpless with this :/