We were facing the same issue after changing the service check interval to 5 min. It seems the agent restarts pull handling after exactly 5 min of inactivity and if the check is attempted during the restart the connection is reset. Changing the interval to any other value fixes it.
**Check worked but only just:**
2022-11-30 20:02:29.686 [ctl:5428] [cmk_agent_ctl::modes::pull][DEBUG] processed task!
2022-11-30 20:07:26.548 [ctl:5428] [cmk_agent_ctl::modes::pull][DEBUG] Got no pull request within five minutes. Registration may have changed, thus restarting pull handling.
2022-11-30 20:07:26.569 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] Start listening for incoming pull requests
2022-11-30 20:07:26.590 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] Listening on [::]:6556 for incoming pull connections (IPv6 & IPv4 if activated)
2022-11-30 20:07:26.716 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] [::ffff:IP]:60268: Handling pull request.
**Connection was reset on the first attempt, retry 1 min later worked:**
2022-11-30 20:13:28.248 [ctl:5428] [cmk_agent_ctl::modes::pull][DEBUG] processed task!
2022-11-30 20:18:26.516 [ctl:5428] [cmk_agent_ctl::modes::pull][DEBUG] Got no pull request within five minutes. Registration may have changed, thus restarting pull handling.
2022-11-30 20:18:26.538 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] Start listening for incoming pull requests
2022-11-30 20:18:26.559 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] Listening on [::]:6556 for incoming pull connections (IPv6 & IPv4 if activated)
2022-11-30 20:19:26.588 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] [::ffff:eyepee]:34222: Handling pull request.
**Perfection:**
2022-11-30 20:40:29.986 [ctl:5428] [cmk_agent_ctl::modes::pull][DEBUG] processed task!
2022-11-30 20:44:56.646 [ctl:5428] [cmk_agent_ctl::modes::pull][INFO] [::ffff:yippee]:38832: Handling pull request.