In Jonathan Littell's novel Les Bienveillantes (English title: The Kindly Ones) the fictional protagonist meets, in 1943, a man employed with the Aktion T4, the organization behind the "euthanasia" murders. In the novel, this person claims that he had killed disabled German soldiers on the eastern front in '41 & '42 (IIRC using a gas van). I'm not sure if the book specifically mentions wether the victims needed psychatric hospitalization, care for physical diabilities or both.
Until 1941, around 70.000 people where murdered in the Aktion T4*. Around 5.000 of these where traumatized Veterans of WWI (Doctors would claim their condition was in same way inherited, german link) Then the murders were officially discontinued, but in reality continued using different means. Many of the key personnel where sent to the newly occupied areas to aid the in the Shoa. So far Littell's version fits the facts known to me. However I had never heard of the Nazi regime killing it's own in this way.
In general, Jonathan Littell seems to have put a huge amount of research into his novel and I'm not aware of criticisms that he got major facts wrong. However, if true it would underscore points made by Browning and Aly in books I've read so it's surprising to me that I never heard about it.
Did the Nazis murder disabled, maimed or heavily traumatized soldiers on the eastern front, using personnel and methods from the Aktion T4?
When and How did this project start and end?
*AFAIK the name Aktion T4 was not used during the war.