transport_ws : transport_poll_write timeout before any socket was ready

[spirinox35]

I'm working on a project integrating an ESP32 connected to an LTE modem, with the aim of communicating with a server via a websocket link. I've integrated the websocket_client component and I'm able to establish a link with my server and exchange data. However, for some reason, when the transmission takes too long (a few minutes), my application seems to get stuck in the esp_transport_ws_send_raw function. After a few seconds, I can see a succession of Error transport_poll_write, with a Timeout before any socket was ready. Moreover, the esp_transport_ws_send_raw function never returns its error. What is the cause of this problem?