Rendering seems to depend on data that is sent by the server (AI?). If the server can not keep up with the clients frame rate, the graphic FPS go down. This is also true for high latency or jitter. Whatever the client is waiting for should be in its own thread not affecting the render loop.
Lag is enough of an issue, tying it to your (graphics) FPS just makes things worse.
tl;dr seperate the render loop into render and update-state-with-received-data loop