I'm running Photo Mechanic Version 5.0, build 16438 (e61be25) on a Retina iMac with OS 10.10.2 at the moment...
I did a search in the Support forum and it seems this problem has afflicted some users back to 2009 with earlier OS X & PM versions.
If PM 5 is up and running the iMac will fail to automatically enter sleep mode when it's reached the time set in the control panel of the OS for iMac to go to sleep.
If I shut down PM5 then it will enter sleep mode as it's supposed to.
It's not an earth shattering crisis, but I have my system do it backup in the middle of the night and if I fail to shut down PM5 before I finish work for the day the system and all the hard drives will remain up and running all night.
The system will enter sleep mode if I do it manually with the command under the Apple Menu but after it's awakend to do the backup PM5 will prevent the system from sleeping at the conclusion of the backup.
I'd sure like to prevent that 6-8 hours of wear & tear on the hard drive array when I fail to close PM5 not to mention the energy savings - It does add up.
Any thoughts?