Could be a tactical issue but most of the times, its down to the players and the man management. They can lack in concentration oand/or get too relaxed after a goal.
Not that I have noticed, they either seem normal or motivated, I don't often see them complacent or relaxed.
I mean, i'm doing pretty well at the moment. 2nd place behind Lille by 1 point. Most wins in the league, and have the third least conceded goals but the majority of them come from this issue. I hope as my squad gels better it will sort itself out.
It has now happened in 5 games in a row. I think my problem is that I through leads away too easily, as I have just done. I was away to Stade de Reims and up 3-1 at half time only to lose 4-3. Really frustrating.