Shirer was the Hearst Newspaper & later, tge CBS radio correspondent in Berlin from 1934 until he “advised” to leave in early 1941. Having read Rise & Fall as well as “Berlin Diary” I have no doubt that his report is true.
See my response above, although Hitler was probably even at that point being pumped up by the infamous Dr. Morel who was his enabler and provider for the cocktail of drugs he was known to take in his time as Chancellor, so, I find it hard to discount nearly any bizzare behavior.