The Benin international was unsettled last year, before agreeing a new long-term contract in August.
O'Neill admits there was an issue, and concedes that could become a problem again - despite the fact he is currently in superb form.
"Stephane was definitely unsettled because his wife and children were living elsewhere," O'Neill told The People.
"We made every effort to sort this out and he got his new contract which is fine.
"A new contract will always settle a player down for a while, but that's not to say there will not be a similar concern in the summer.
"But at least he has settled down and he is back enjoying football again and when he is he is sparkling."