In order to identify the issue/problem that you encounter during bare metal deployment, you need to check the VmmAgentPE.exe.log before reboot the server.
Press Shift + F10 to open a command prompt
navigate to x:\vmm folder and create a copy of vmmAgentPE.exe.log to x:\vmm\error.txt. Once it has successful create a copy, open the error.txt.
Read and identified the issue that you face.
Hope this give you a clear idea of why the bare metal deployment is failed when using VMM 2012. Good luck.