I'd be interested to know from regular U23 watchers where Buckley tended to play when he was a star performer for that team. For the first team, he seems to play as a deep-ish lying fulcrum midfielder, when in midfield, which doesn't seem to suit him. Recently, Mowbray described him as an attacking midfielder who glides past defenders in training. That's not something that has been seen in first team matches.
I am not ready to give up on Buckley, given his success at U23 level and the occasional glimpses he has shown, especially, initially - but he does need improvement and, perhaps, a fixed position that suits him would help. Joe Rothwell has come more into his own since finding a role best suited to his game.
Mowbray turned down League One loan enquiries in September, last year, but, if there was such an option now, I think it might be for the best for Buckley. If he stays, he should get regular U23 games to prove his worth again and build confidence.