As of today (Jan 05) the builds of Jenkins core deployed in Code Valet are starting to log "Collision detected. timestamp=1515197742000, expected=1515193821000 "
It's unclear to me why this is happening but this log message has never been spotted before in Code Valet and is starting to crop up on completely idle master instances.
I think this might be a "canary" chirping that something is wrong with some recent changes in master but I haven't the slightest idea what they might be. Perhaps Oleg Nenashev knows?