pbs[898]: BUG in libdispatch client: kevent[mach_recv] monitored resource vanished before the source cancel handler was invoked

You may notice this message in your Mac Console log (System.log file). If your Mac suddenly is having issues with sleep where it does not properly work or is not woken on demand, update to the latest version of Mac OS High Sierra or later.

If this still does not fix the issue, ensure cupsd is not enabled. Cupsd is known to prevent Macs from sleeping.