Steps to reproduce:

1. Create and configure active proxy on separate node, set up it in Zabbix frontend, assign some hosts and items, update configuration cache for proxy, ensure, that data is coming
2. Run force cache reloading for zabbix-proxy
3. In the same time - drop incoming connection on zabbix server (firewall/link down, etc)
4. Wait for connection timeout+ 5 minutes
5. Restore the connection

Result:
Zabbix proxy configuration syncer in constantly busy until next successful configuration cache update
Expected:
Configuration syncer is not not busy when connection is lost

Looks like self-monitoring process bug

Screenshots attached