Steps to reproduce:

1. Since Update from Zabbix 4.0.0 to 4.0.2
2. "Zabbix housekeeper processes more than 75% busy" is for hours a warning

Result:
watch -tn 0.2 'ps -fC zabbix_server | grep housekeeper'
Shows this:
zabbix     639   502  0 Dez11 ?        00:00:06 /usr/sbin/zabbix_server: housekeeper [removing deleted items data]