Hi,
We have sent an upload url via a private message.

Sockets in CLOSE_WAIT are unexpected, because it means that the system has detected a closed socket but the Server has not yet detected it.
The Server usually keeps the sockets monitored.
One possibility is that there are delays in the initial handling of client requests. This should be visible in the logs.
The fact that so many sessions have been established with far fewer clients is a sign that there is an underlying issue.