R220 BitLocker TPM Network Unlock

Good morning,

We are trying to roll out BitLocker to our Dell R220 servers. Part of this requires the use of Network Unlock (new feature in Server 2012 R2) to minimise downtime to services.

We have configured successfully the Network Unlock role, certificate etc. Network unlock works fine for a client machine.

We have encrypted a Dell R220 using TPM and BitLocker. On a cold boot of the server, BitLocker unlocks on the network and boots Windows as we want it to. On a warm boot of the server, BitLocker prompts for a PIN and Recovery Key. So far, I have;

Performed full firmware and driver update (BIOS 1.4)
Performed full Windows Update
Decrypted/Re-encrypted the drives
Enabled & disabled Intel TXT

Is there a way I can disable warm boot and force a cold boot on every restart?

Is there a setting somewhere that I have missed? 

Thanks

Mark