Reviving this thread… I have one of these basses. (It's my only bass, actually.) Thought that I'd provide some info that might be useful to others.
The bass was OK, but it needed some help to be more playable. So I dropped the bridge down to the body. And added some shims to the neck pocket. I put two business cards in there, of different lengths, to add some tilt. Got the thing playing well, with the action nice and low. All was well.
(An aside: This was actually the first time that I ever removed the neck of any guitar or bass. I was able to do it without needing new strings. I loosened all the strings until they were super floppy but still in the tuners. Then wrapped a face cloth around the neck and held the strings to the neck with a woodworking clamp. Removed neck, added shims, put the neck back on, removed the clamp, tightened the strings. Excellent.)
So the bass is playing well. I got away from playing for some months. Switched over to guitar. Roamed the Earth for while. (OK, it was work travel.) Then one day, I look at the bass and the strings are a mile high off the fret board. Just like Chuck King said, above. The neck took on a little curve, for the first time. So I removed the neck as described above, gave the truss road about a 1/3 turn (4 mm Allen wrench, BTW). Added two more business card shims, for a total of 4 cards in there now. Put the neck back on. It's better for sure. But not where it was earlier and not quite to where I want it to be.
I looked closely and do not see any warping of the body. But I did see what is in the photo, below. It seems as though the bridge screws are tearing themselves out of the body. Or, actually, the metal that the screw sits in. Uh oh!
Next up, I think that I will try adding a wood shim into the neck pocket, something in the range of 0.1"/2+ mm thick. Might help. Although I am likely be fighting a loosing battle here.
I do like the sound of the bass. But it has a flimsy feel to it. Note in the photo how even the bridge metal has a warp to it. And playing the first fret requires a bit of reach. Now I think I can see where the cheapness of it all is playing out. I may have to get a "real" bass next. Still, I'm glad that I have it here, to play a little bass when the urge strikes.