Could you please verify if the E20 is allocating an MTP from CUCM? There an option on the E20 config profile that will force an MTP to be requested on every call that is "Media Termination Point Required".
The MTPs don't support video codec, only audio codecs.
hmm, The issues I knew about were fixed in TE4.. so that rules them out. TE4.1.2 is the latest released, so it might be worth trying that if you can.
So the problem was related to another issue related to Jabber video in deskphone mode. After it was solved this started working also without any configs on the E20.
Here is the link: