One thing about Walmart Bikes is that the quality of assembly is often terrible. They are store employees, not mechanics. When assembling a bike, failing to properly torque everything, using loctite, etc, will lead to premature failures. Even a crappy bike properly assembled should last a little while. There is a video of a guy taking a Walmart bike down the downhill track at Whistler, other than melted brake pads the bike bike survived. He did all the things I mentioned, including tightening the spokes
However, since you are already in the position of having failures, a better bike is probably a good idea.