All nodes are periodically unavailable through Zabbix Proxy. What could be the problem?

Question

Zabbix

Good afternoon.

There are several Zabbix Proxies that are connected to the Zabbix server.
There are 10 nodes behind one of the proxies. Recently, with a frequency of 5-10 minutes, triggers began to arrive from this proxy, stating that all nodes are unavailable.
Looked into the proxy logs. I saw this picture:
- Unable to connect to the server [ip_zabbix_server]:10051 [cannot connect to [[ip_zabbix_server]:10051]: [110] Connection timed out]. Will retry every 1 second(s)
- Connection restored.

What could be the problem? Has anyone come across?

thanks in advance