Steps to reproduce:

1. Active agent checks
2. Run command:  zabbix_server -R log_level_increase && zabbix_server -R log_level_increase && sleep 420 && zabbix_server -R log_level_decrease && zabbix_server -R log_level_decrease
3. Wait 5 minutes.

Result:
After 5 minutes there are massively triggered "Agent unreachable" triggers. But, at the end, after double decreasing log level, triggers statuses returned to OK.
Expected:
Runtime control increasing log level must not affect Zabbix agents checks at all.