Fan Blade Wobble or Part of the Design?
The problem you are getting is due to a warped fan blade, assembly of motor, or unbalanced spin radius. Your best bet on this is to seek a replacement from your manufacturer, as this is likely a fault of the assembly process, or even of manufacturing the fan blade set anyway.
While the problem is not a major one, and you will be just fine using said fan for some time, it will shorten the life of the motor, which will eventually run dead due to extra stress. To prevent excess wear and tear, run the fan at a slightly lower speed, i.e. on 2, maybe even 1. At higher speeds, the centripetal force will cause the blades to warp further, and pull the motor back and forth, and thus, cause the unit further damage.