The Funfactor wheels are a bit sloppy from stock. Not sure if you've done this already, but if you take and put a 10x15x4 bearing (better double check on size wtih someone, or do a search on the forum) Inside the hub where the shaft goes through, without removing the original bearing(so you will have 2 bearings on the inside of the hub) You will remove a lot of wheel slop.

you do need to be fairly cautious when tightening these up because you can break or strip shafts.
I'm not sure if it's a warranty thing unless tha part was really flimsy and defective, but go to www.cenracing.com and you should find a customer service section with some phone numbers and emails.