It is a pain to deal with, but the Autoboot user account is an option you can try. What happens is this:
1. You Enable the $Autoboot$ user (make sure it has already been added to the machine) 2. Uncheck the box for the machine that says "Disable checking for Autoboot" 3. Force a sync to the machine
If all is good with the sync, the next time the machine reboots it will completely bypass the PBA and boot to the OS (and subsequent reboots until you change it back).
Once done rebooting, you should Disable the Autoboot user again and re-check the "Disable checking for Autoboot". (I use both methods to be sure)
There are ways of changing the Autoboot account, using different names like $autoboot$US, or changing the default password from 12345 (requires a client change though - i think the sdmcfg.ini).
Don't bother creating multiple different autoboot accounts and applying them all to every machine. The boot process only looks for and uses the first autoboot it finds and ignores the rest - found that out the hard way (version 5.1.9).