IMO all spiders and womas have a wobble to some degree. I have a male spider who has the worst wobble I have ever seen. He literally corkscrews and ties himself up all the time. He even lays on his back completly still (making me think hes dead). I have had him for going on 3 years now and although he will never be bred (personal preference), he eats just fine.
EDIT: I would actually applaud the seller for disclosing the wobble to you. I know when I bought my spider they didnt tell me anything. Id be more inclined to buy from a honest seller...