I don't have a blog to put this on, so I will put it here. Maybe Google will index it and it can help someone later.
If you have an existing VMM server and then install App Controller to it, things will cease to work. You will just get a cryptic 2912 errors with NO_PARAM: NO_PARAM and unknown error.
This mostly shows because you can't deploy templates and if you try and join a new host to the VMM server, it will fail.

There is a hint in the error though:
http://schemas.microsoft.com/wbem/wsman/1/wmi/root/microsoft/bits/BitsClientJob
It is a BITS error. I even read this a couple of times while troubleshooting and it didn't twig why it had happened. Instead I chased certs, user accounts, network and almost reloading the Host I was trying to add out of frustration.

BITS runs on port 443 for VMM by default.
If you install App Controller, it puts a website for management slap bang onto port 443. This breaks BITS.

The fix:
Go through all Library servers, Hyper-V Hosts and the VMM Server and change the VMM BITS port to something else like 8500 using regedit.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft System Center Virtual Machine Manager Server\Settings and the key is BITSTcpPort.
For library servers and Hosts go to
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft System Center Virtual Machine Manager Agent\Settings and the same key.
Then you can restart the VMM service or reboot the VMM server and hosts depending on how much you need the uptime.
http://social.technet.microsoft.com/wiki/contents/articles/18465.vmm-2012-change-bits-port-used-for-template-provisioning-bits-over-https.aspx

Any future Hosts provisioned through VMM will use the new port by default.

That is my brain scratcher for today.