Hi maicod, I've got two 112D's and they both burn well and are very reliable.
One of them has exactly the same issue as yours. Not every time, but sometimes when I go to close the tray using the eject button it sticks a little and the tray doesn't go in. Anyway when it does happen all it ever needs is a very gentle nudge with my finger and it goes straight in. So really this hasn't caused me any grief and I'm certainly not worried about it.
One day I might pull it apart and give it a bit of a clean and lube, but it's not a priority. I can certainly live with it as it is. It doesn't effect the burn quality in any way and I don't think it is any indication of the drives imminent demise.
BTW. Does yours also go straight in with just a little nudge or is it a more serious sticking problem?