Active checks availability indication became unknown for host which is assigned to active proxy

Steps to reproduce:

1. Create a proxy
2. Create a host with active check item
3. Assign the host to the proxy
4. Run proxy, server, agent
5. Observe that active check availability indication has available status
6. Wait for a ~20 min
7. Observe that active check availability indication became unavailable

Result:
Active checks availability indication became Unknown after approximately 20 min of run of the instance for host which is assigned to active proxy. However data continue to gathering. Switching host to "no proxy" and assigning proxy again makes indication Available again.

zabbix_proxy.log.tar.gz  zabbix_agentd.log.tar.gz

Expected:
Active checks availability indication has available status.