Sorry forgot to mention - this could be a hibernate type sleep mode. It takes a while to boot to the previous spot where it was when it does go to sleep and I see quite a bit of SSD activity so when I say sleep I could very well mean hibernate.....
Disabling some of the power options in BIOS may be of help.
Is there any difference in the process you ran with the first units and these last ones? Are the units different somehow (BIOS version, SA number, operating system version)?
Would it make a difference if you do not update the BIOS before running OOBE mode?
You may also contact Microsoft* about this issue.