Is he still stepping up and coming out when you ask? Any other behavior changes? More beaky or bitey?
How long have you had him? Is he showing interest in toys and food? Any chance he's showing interest in a sexual way for toys, rope perches, any bins or baskets in his cage?
And are you positive he's a him? If there are no signs of not feeling well, it could be sign of hormones. One of the small girls prefers to be in her cage / nest....