Can't submit a birth date for Douglas Hodge nm0388061

Douglas Hodge nm0388061 is listed as having a birthdate of 25 February [no year]. I have evidence of his birth year: an article in 2013 that gives his age as 52, published on 6 February 2013 so just before his birthday, hence his birth year is 1960, not 1961 as simple maths 2013-52 would suggest. However... when I try to edit his DOB, only the place is listed; I cannot correct or add to his date of birth. Is this a bug or is the DOB intentionally locked? The supporting article is https://www.independent.co.uk/arts-entertainment/tv/news/only-fools-and-horses-actors-tessa-peakejones-and-douglas-hodge-split-up-after-27-years-together-8483294.html - article date "Anthony Barnes Wednesday 06 February 2013 13:34 GMT" and "Hodge, 52, has been prominent mainly on stage"