If the number of characters in the OEMPnPDriversPath entry of the Unattended.txt file exceeds 256 characters, the registry will be missing some information, causing some device drivers to NOT be automatically installed.
To workaround this feature:
1. Open the Hivesft.inf file in the distribution share.
2. Locate the HKLM,"SOFTWARE\Microsoft\Windows\CurrentVersion","DevicePath",0x00020002,"%SystemRoot%\inf" line.
3. Modify this line to include as many additional driver locations as you require, separated by a semi-colon (;).