Wonnlefoot - If you buy cheaper T/T's like the ones mentioned, you are always in danger of buying a dud, but 4 of the trot is difficult to achieve, but as you found out not beyond the realms of possibility. The manufacturers work with cheaper components and cut cost due to economics, however if the company does not have a established Statistical quality engineering set up, they will not have the knowledge & techniques to reduce variation in the components. No company can inspect quality into their products, the car industry found that out in the late 70's when superior build Japanese cars arrived on the market.
I would like other people have suggested look to get a Technic's, as they have been going with a lineage of T/T like the SL1200 for quite a while now. Companies with a proven track record are always a better bet.
Cheers