Yep. And you were probably right:
2020/12/14 12:38:17 [notice] 57790#57790: signal process started
2020/12/14 14:16:00 [alert] 57791#57791: *218 open socket #29 left in connection 3
2020/12/14 14:16:00 [alert] 57791#57791: *219 open socket #36 left in connection 16
2020/12/14 14:16:00 [alert] 57791#57791: aborting
2020/12/14 14:16:21 [notice] 67283#67283: signal process started
2020/12/14 14:16:29 [error] 67284#67284: *8 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: site1.local, request: "GET /socket.io/?EIO=3&transport=polling&t=NPXPIv5 HTTP/1.1", upstream: "http://127.0.0.1:9000/socket.io/?EIO=3&transport=polling&t=NPXPIv5", host: "localhost", referrer: "http://localhost/desk"
2020/12/14 14:16:31 [error] 67284#67284: *8 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: site1.local, request: "GET /socket.io/?EIO=3&transport=polling&t=NPXPJED HTTP/1.1", upstream: "http://127.0.0.1:9000/socket.io/?EIO=3&transport=polling&t=NPXPJED", host: "localhost", referrer: "http://localhost/desk"
2020/12/14 14:16:35 [error] 67284#67284: *15 connect() failed (111: Connection refused) while connecting to upstream, client: 127.0.0.1, server: site1.local, request: "GET /api/method/frappe.realtime.get_user_info?sid=c50a774724f8422547fee875e0536e0c242bc894f17f4987170732d9 HTTP/1.1", upstream: "http://127.0.0.1:8000/api/method/frappe.realtime.get_user_info?sid=c50a774724f8422547fee875e0536e0c242bc894f17f4987170732d9", host: "localhost"
2020/12/14 15:20:39 [notice] 8229#8229: signal process started