Dfariswheel is correct, sort of. There are no "good" or "bad" years in firearms production, not in specific companies or in general. But there are periods when a company, for whatever reasons, allows its quality control to slip or its production quality to decline. That might be due to worker morale, union problems, strikes, speeded up production, worn out machinery that can't be replaced, lack of liquid capital, and/or more.
The first quality control has to begin with the individual worker. He or she must spot the badly machined part, the wrong temperature in the heat treating, the poor polish job on the frame. By the time a product gets to final inspection, it becomes very expensive to fix problems and there is a tendency to "let it go."
What can companies do? The list of problems pretty well includes the solutions. But solutions are easy to determine, not so easy to implement, so we will continue to have "good" and "bad" periods. As an example, there has been a lot of criticism of a certain foreign company over QC issues. Their designs are first rate, their materials the best, their machinery world-class, yet their production workers and inspectors either are not motivated or aren't paid enough to really care about quality. The result is a large number of complaints, an overwhelmed Customer Service, and loss of repeat buyers.