Today on one device I noticed error in ZCC "KB validation failed, inventory scan can't be started". In log I saw reason – "SW.KB - file not found, KB validation failed". How that could happen? Meaning, missing SW.KB? Probably fail "Knowledge Base Files (3.6.A.4.16)(02-Jul-2015) (INSTALL)".
Copied this missing file from another device, hopefully it solves problem for now.