There are two alternatives to solve issue customizing properly GPO:
You can do this with Group Policy, using the Always wait for the network at computer startup and logon policy setting.
https://technet.microsoft.com/en-us/library/gg486839.aspx
Alternatively adding a delay during policy appling this policy:
Policy Location: Computer Configuration > Policies > Admin Templates > System > Group Policy
Setting Name: Startup policy processing wait time
Registry Key: HKLM\Software\Policies\Microsoft\Windows\System!GpNetworkStartTimeoutPolicyValue
https://support.microsoft.com/it-it/help/2421599/windows-7-clients-intermittently-fail-to-apply-group-policy-at-startup
