Friday night, the billionaire entrepreneur Elon Musk appeared in front of a cheering and adoring audience, much like a rockstar appears on stage before performing a show, to unveil the new Model 3 Tesla. The event was to celebrate the first 30 customers (all Tesla employees) getting their Model 3's.

Early production has been slow, but Musk expects to be able to produce 20,000 Model 3 Teslas per month by December. Ramping up production is going to be brutal, Musk warned.

"We're going to go through at least six months of manufacturing hell," the Tesla CEO told a group of journalists ahead of the Model 3 event. On stage, Musk echoed the sentiment.

According to the Fremont, Calif., factory workers, Tesla is already putting its employees through a lot.

"One of the most serious issues concerns our health and safety," says a letter a group of factory workers from Tesla's main Fremont, Calif., facility submitted to the independent board members of Tesla on Monday, just three days after the Model 3 event and amid an ongoing effort to unionize.

"Accidents happen every day. Severe incidents frequently impact morale and cause delays in production. We are losing great workers who are valuable to both our production team and to their families while they spend time on medical leave, recovering from preventable injuries."

In May, California-based worker safety organization Worksafe published an extensive report after it analyzed the log of work-related injuries and illnesses at Tesla.