SSL_write() failed (104: Connection reset by peer) while sending to client

I have seen the following error in the log of Kong:
2023/06/01 15:27:37 [info] 1103#0: *6972 SSL_write() failed (104: Connection reset by peer) while sending to client, client: 11.11.11.11, server: kong, request: “GET /xapi/v1/api/xyz/export HTTP/1.1”, upstream: “http://10.10.10.10:3100/v1/api/xyz/export”, host: “xyz.xyz.com”, referrer: “https://xyz.xyz.com/xyz/xyz

This happens when the backend service spends several minutes to prepare a file for exporting.
Kong is v2.6.0

Can you please explain to me what is happening here? What should be the possible cause of this connection reset. And who resets the connection? Any suggestion about the next steps to take in order to fix this.
I appreciate you time.

Thank you.