Final inspection probably wouldn't catch something like that. By the time it gets that far, the machine is fully assembled and the defective part is hidden from view. The inspector would at best operate the cross slide and find it working. In fact, the bias might even improve the operation by removing some backlash. Chinese workers have apparently not been trained to do in-process inspections. Or it may be that they are working piecework and paid according to the number of operations completed in an hour. Removing a defective part and replacing it with a new part would cut into the production.
Part of the blame has to rest on the shoulders of the importers. Grizzly and Tormach, to name a few have all brought equipment with hidden defects into the country. They claim to have quality control inspectors working in both the country of manufacture and stateside but defects keep getting past them. I have machines from both Tormach and Grizzly and have found manufacturing flaws in every machine purchased from them. None of the machines were inspected stateside.
This problem isn't exclusive to Asian machines. Made in USA doesn't guarantee quality. The quest for squeezing every last nickle out of production costs takes its toll. There was a time when a workman would sign his name with pride on his work. That doesn't exist any more. ISO9000 makes an attempt to solve these problems with its continuous quality improvement philosophy and if practiced properly, would do so but often the manufacturer's objective is to pass the audit and get the certification.
When a new home is built, building inspectors inspect at every step of the way rather than coming into the completed home and stamping "Approved" on the final sign off. This is done to uncover defects that would otherwise be hidden by following work. The same should be done in factories at all steps where further assembly would hide a defect. Workers would be trained to inspect the parts that they are using and reject those not meeting standards. It would add cost to the production but when weighed against the cost of dealing with returned goods and lost customers, probably be a wash.