RTSP not available after some time - 503 Service Unavailable

[mordka]

I'm working with a customer running FortiGate 500E that is routing requests to RTSP camera. Everything works great but after few days the camera is not responding on port 1935.

method OPTIONS failed: 503 Service Unavailable
Server returned 5XX Server Error reply

However the camera works fine on port 80 - I can access the web portal and watch the stream. I can restart the camera and after this, the port 1935 is available again which solves the problem temporarily.

I don't have access to fortigate portal so I'm reaching out for help here. Could it be caused by rtsp session helper? Is there a limit that we may be exceeding?