After upgrading zabbix to 3.0 we catch issue with zabbix_server stability
In random time, after server bootup zabbix_server get hungs and won't work with agents
On Agent side in the same time, i see messages like:
active check data upload to [X.X.X.X:10051] started to fail ([connect] cannot connect to [[X.X.X.X]:10051]: [4] Interrupted system call)

If i restart server, problem was fixed for some time.