The bearings probably just need a bit of adjustment – You can tighten up the bearings in the same way as a cup and cone hub, but they are *very* touchy to get just right (IME). The locknuts on one spindle were left-handed on mine, despite the instructions saying that they were both right-handed (IIRC, the left-handed nuts had notches around the outside).
The spindles are the same/similar to other Shimano pedals – about 11 minutes in for the bearing adjustment (I have dismantled mine, but wouldn’t bother again – just adjust / re-grease as shown):
I found that it needed a bit of trial and error to get the right balance between smoothness / play with the bearing refitted to the pedal.
ETA: Slightly better video on the adjustment (but still with an irritating introduction)