Configuration syncer can give the following error when syncing configuration cache:

zabbix_server [29582]: ERROR [file:dbconfig.c,line:2115] Something impossible has just happened. 

This might happen when a host with interface is added during configuration cache synchronization betweem host and interface sync. The error message is harmless, but still should be handled differently. One way would be to skip processing interfaces without hashed hosts (like it's done with items).