group policy fails to apply to 25% of computers

group policy not applying consistently across a group of computer with the same image and in the same office.

-we are a library of around 500 or so staff computers and utilize group policy to push out all sorts of things.
-recently we decided to push office2013 through group policy to all of the staff pc's throughout the domain (domain consists of hq-about 200 pc's within 10 departments, and 11 branch libraries scattered throughout the county)
-all of the staff pc's have the same image
-say I decide to push office2013 to department "a" tonight.
-department "a" contains 15 computers (with same image)
-I set the policy and ensure that all of the pc's are in the proper ou and apply the gp
-I send an email to department "a" telling them to reboot their pc's prior to going home for the day
-when I check the pc's in the morning, all but 3 of the pc's have office2013 installed
-I reboot (just in case the staff members forgot to the night before, but still no go)
-if I go into the nic properties and give it a static ip address, along with the ip addresses of the dns servers and then reboot, the group policy applies
-this always works
-but if I do not give the nic a static ip and just keep rebooting the pc to see if the group policy will apply, it will not, no matter how many times I reboot.
-yes I have tried "always wait for network at computer startup and logon"
-tried setting "startup policy processing wait time" to 120 seconds

any thoughts?