You need to align the lens and negative stages to quite a bit of accuracy.

I don't own this enlarger, but someone who does posted this method of alignment:
John Frank , Sep 08, 2005; 11:28 a.m.
Here's the answer for anybody interested...first level the enlarger column by adjusting the legs of the enlarger. Then level the base board using the adjustment screws hidden under the baseboard. (Don't forget to check that the paper easel sits perfectly level on the baseboard too.) Next you must level the lens and negative stages in both the horizontal and vertical planes. To adjust the horizontal plane is easy, each stage just swings around a 'pivot screw' which you must first loosen: the negative stage pivot screw is behind the lever used to lift the head, and the lens stage pivot screw is right behind the lens. These screws are loosen by screwdriver or they may have a 'swan neck' handle on them that you can open manually. To adjust the vertical plane (the angle between the column and the stage) is a bit more tricky. First you have to locate the correct screws. Here's directions: the arms that hold each stage come in three parts, the first is called the 'runner', which is attached to the column. Then there is a middle part, and last of all the actual stages themselves. The screws you want are those that join the middle part to the runner, and you find them by looking up inside the middle part of the arm (you might have to unscrew a small metal plate to see inside the lens stage arm). On the bottom left and bottom right you'll see two big screws that stand out from the surface...these are the locking screws. Right beside them, embedded in the metal you'll find the adjusting screws. There are two steps which involve first loosening the two 'locking screws' per stage and then screwing in/out the two 'adjustment screws' per stage which are located right beside the locking screws. Of course you must lock up again when the stages are level. Remember to adjust the enlarger with the head on and the negative carrier in...'test it as you use it'!