Got the same issue as you. In my case its with Windows 8 (RTM) and Windows 10. I have Windows 8.1 and 7 images that customize just fine. I even upgraded vCenter, ESXi, and VMware tools on images to 6.0 U2 since 1B seemed to start the problem. Still have the issue after upgrading all components. I have not been able to resolve so far.
My log output looks identical:
[2016-03-22T13:18:48: : INFO] GuestCustUtil invoked.
[2016-03-22T13:18:48: : INFO] Params: customize -sealparam "/quiet /generalize /oobe /reboot" -nics 4000 -schedulenativeunobfusc
[2016-03-22T13:18:48: : DEBUG] Registry value 'CustomRescheduleFlags' is not set. Returning default value: 0
[2016-03-22T13:18:48: : INFO] Checking for Windows Sysprep Respecialize operation.
[2016-03-22T13:18:48: : DEBUG] Sysprep process is currently running.
[2016-03-22T13:18:48: : DEBUG] Windows Sysprep 'Respecialize' registry value is not set.
[2016-03-22T13:18:48: : INFO] Windows Sysprep Respecialize operation was not detected.
[2016-03-22T13:18:48: GuestCustUtil: DEBUG] Deleting status marker file C:/Windows/.post-gc-status
[2016-03-22T13:18:48: GuestCustUtil: DEBUG] Status marker file C:/Windows/.post-gc-status doesn't exist
[2016-03-22T13:18:48: : INFO] Extended customization is not enabled!
[2016-03-22T13:18:48: : DEBUG] Customization in progress set to 1 at 2016-Mar-22 13:18:48
[2016-03-22T13:18:48: : DEBUG] Rpci: Sending request='deployPkg.update.state 4 0 C:/Windows/TEMP/vmware-imc/guestcust.log'
[2016-03-22T13:18:48: : DEBUG] Rpci: Sent request='deployPkg.update.state 4 0 C:/Windows/TEMP/vmware-imc/guestcust.log', reply='', len=0, status=1
[2016-03-22T13:18:48: : DEBUG] Successfully opened key SYSTEM\CurrentControlSet\Control\Session Manager\
[2016-03-22T13:18:48: : DEBUG] Size of reg_multi_sz 21.
[2016-03-22T13:18:48: : DEBUG] Read multi_sz value from registry autocheck autochk *, size 21.
[2016-03-22T13:18:48: : DEBUG] string value from registry autocheck autochk *.
[2016-03-22T13:18:48: : DEBUG] Returning 1 elements
[2016-03-22T13:18:48: : DEBUG] Got BootExecute from session mgr.
[2016-03-22T13:18:48: : DEBUG] Native App sysprepDecrypter.exe, arguments ''
[2016-03-22T13:18:48: : DEBUG] Copied file sysprepDecrypter.exe to C:\Windows\system32\sysprepDecrypter.exe
[2016-03-22T13:18:48: : DEBUG] Updated boot execute value.
[2016-03-22T13:18:48: : DEBUG] Successfully created/opened key SOFTWARE\VMware, Inc.\Guest Customization\
[2016-03-22T13:18:48: : DEBUG] New boot execute:
[2016-03-22T13:18:48: : DEBUG] autocheck autochk *
[2016-03-22T13:18:48: : DEBUG] sysprepDecrypter.exe
[2016-03-22T13:18:48: : DEBUG] Temporary sysprep dir path: C:\sysprep
[2016-03-22T13:18:48: : DEBUG] Moving directory 'sysprep' to 'C:'
[2016-03-22T13:18:49: : DEBUG] select * from win32_networkadapter where Manufacturer != 'Microsoft' and ServiceName != 'VMnetAdapter' and manufacturer is not null and MACAddress is not null
[2016-03-22T13:18:49: : DEBUG] Found 1 objects. Pointer 26e4bd0. return code 0(0x0)
[2016-03-22T13:18:49: : DEBUG] Found 0 objects. Pointer 0. return code 1(0x1)
[2016-03-22T13:18:49: : DEBUG] Returning value 00:50:56:9D:72:70 for system property
[2016-03-22T13:18:49: : DEBUG] Setting dhcp for nic # 0
[2016-03-22T13:18:49: : DEBUG] Returning value \\WIN8X64-TMP\ROOT\CIMV2:Win32_NetworkAdapter.DeviceID="10" for system property
[2016-03-22T13:18:49: : DEBUG] ASSOCIATORS OF {\\WIN8X64-TMP\ROOT\CIMV2:Win32_NetworkAdapter.DeviceID="10"} where ResultClass = Win32_NetworkAdapterConfiguration
[2016-03-22T13:18:49: : DEBUG] Found 1 objects. Pointer 26e8dc8. return code 0(0x0)
[2016-03-22T13:18:49: : DEBUG] Found 0 objects. Pointer 0. return code 1(0x1)
[2016-03-22T13:18:49: : DEBUG] Clearing gateway ip addresses.
[2016-03-22T13:18:49: : DEBUG] Enabling DHCP on the computer
[2016-03-22T13:18:49: : DEBUG] Returning value \\WIN8X64-TMP\ROOT\CIMV2:Win32_NetworkAdapterConfiguration.Index=10 for system property
[2016-03-22T13:18:49: : DEBUG] Setting DNS Server to ip
[2016-03-22T13:18:49: : DEBUG] Resetting NIC's static IPv6 settings...
[2016-03-22T13:18:49: Netsh: DEBUG] Fetching adapters information...
[2016-03-22T13:18:49: Netsh: DEBUG] Interface 14 is not found
[2016-03-22T13:18:49: : WARN] Resetting NIC's static IPv6 settings has failed. Ignoring
[2016-03-22T13:18:49: SysprepDriveLettersWorkaround: DEBUG] Backing up HKLM MountedDevices before sysprep runs
[2016-03-22T13:18:49: : DEBUG] Enabling SE_BACKUP_NAME privilege
[2016-03-22T13:18:49: : DEBUG] Retrieving process access token for SeBackupPrivilege
[2016-03-22T13:18:49: : DEBUG] Getting LUID
[2016-03-22T13:18:49: : DEBUG] Adjusting privileges
[2016-03-22T13:18:49: : DEBUG] Backing up SYSTEM\MountedDevices to C:\sysprep\MountedDevicesBackup
[2016-03-22T13:18:49: : DEBUG] Executing command C:\windows\system32\sysprep\sysprep.exe /quiet /generalize /oobe /reboot /unattend:C:\sysprep\sysprep.xml
[2016-03-22T13:18:49: : DEBUG] Successfully executed command C:\windows\system32\sysprep\sysprep.exe /quiet /generalize /oobe /reboot /unattend:C:\sysprep\sysprep.xml
[2016-03-22T13:18:49: : DEBUG] Trying to connect network interfaces, attempt 1
[2016-03-22T13:18:49: : DEBUG] Rpci: Sending request='deployPkg.update.state 4 103 C:/Windows/TEMP/vmware-imc/guestcust.log@4000'
[2016-03-22T13:18:49: : DEBUG] Rpci: Sent request='deployPkg.update.state 4 103 C:/Windows/TEMP/vmware-imc/guestcust.log@4000', reply='queryNicsSupported', len=18, status=1
[2016-03-22T13:18:49: : DEBUG] Got VMX response 'queryNicsSupported'
[2016-03-22T13:18:49: GuestCustUtil: DEBUG] Status marker file C:/Windows/.post-gc-status doesn't exist
[2016-03-22T13:18:49: : DEBUG] Rpci: Sending request='deployPkg.update.state 4 104 C:/Windows/TEMP/vmware-imc/guestcust.log@4000'
[2016-03-22T13:18:49: : DEBUG] Rpci: Sent request='deployPkg.update.state 4 104 C:/Windows/TEMP/vmware-imc/guestcust.log@4000', reply='disconnected', len=12, status=1
[2016-03-22T13:18:49: : DEBUG] Got VMX response 'disconnected'
[2016-03-22T13:18:49: GuestCustUtil: DEBUG] Status marker file C:/Windows/.post-gc-status doesn't exist
[2016-03-22T13:18:50: : DEBUG] Rpci: Sending request='deployPkg.update.state 4 104 C:/Windows/TEMP/vmware-imc/guestcust.log@4000'
[2016-03-22T13:18:50: : DEBUG] Rpci: Sent request='deployPkg.update.state 4 104 C:/Windows/TEMP/vmware-imc/guestcust.log@4000', reply='connected', len=9, status=1
[2016-03-22T13:18:50: : DEBUG] Got VMX response 'connected'
[2016-03-22T13:18:50: GuestCustUtil: DEBUG] Status marker file C:/Windows/.post-gc-status doesn't exist
[2016-03-22T13:18:50: : INFO] The network interfaces are connected on 1 second
[2016-03-22T13:18:50: : INFO] GuestCustUtil exiting.