Think i should replace the nut?
If the string saddles on the bridge are very far forward it might just be the spring rattling. The bass is probably fine don't take it back unless you wanna be a weenie. Most of these I've played are pretty awesome (if yer ok with condoning slave labor) and a pro setup likely will solve yer problems. Spend $50 and get a good tech to set it up and if it really does suck and needs to go back he'll tell you. Try to decide what strings you want to use first as this has major effects on the intonation and truss rod adjustments.