Networkmanager reply never returns in Release builds

I have a qt cmake project and use qt creator.

In Debug builds everything works fine, i receive the data from my api. But when i set the build type to "Release" then the networkmanager just freezes and never returns a reply:

auto m_manager = new QNetworkAccessManager(this);

QNetworkReply* reply = m_manager->post(request, postData);

connect(reply, &QNetworkReply::finished, this, [=,this]()

{         // In Release builds it will never be called     // In Debug builds this works fine }

);