This is a strange phenomenon, because conditions in the factory improve every year, so the employees should have been much more upset a couple of years ago, when they began building the Model S, later the Model X.
A more reasonable explanation for the sudden whining could be that the workers feel their jobs threatened, as Tesla purchased Grohmann Engineering GMBH, which specializes in automation. This relatively small company will supply all robots for future Tesla production lines, including Solar Roof, Model 3, Y ... Tesla Semi ...etc. They even cancelled all projects for other factories, which were in the works before Tesla purchased them... now they only work for Tesla, and it seems they'll have a lot to do, as Tesla is planning to open at least 4 Gigafactories in the near future, on different continents.
To give you a picture about how much automation matters, right now in the Tesla Gigafactory 150 workers produce about 20 battery packs per day for the preproduction Model 3 cars. Tesla is investing 215 million USD in robots, which will reach a 75% efficiency and produce almost 1000 battery packs per day.
This is a Model S battery pack. The Model 3 battery pack is very similar, but it's smaller, uses larger (21700 vs. 18650), fewer battery cells ... and also an improved thermal management system...
Some websites predict that Model 3 battery packs will have 50% less cells than Model S, which may have implications in charging speed and total power output to the motors. We'll have to see in a couple of months, when the first customers (Tesla and Space X employees) will receive their Model 3s.