According to the union's statement, a third of all workers is on sick leave at any given time due to workplace injuries. They're also paid below union rate despite claims to the contrary by Tesla management. Tesla also tried to preempt a union recruiting event by giving the workers free pea soup so they'd stay in throughout the lunch break and not talk to the union reps waiting outside the factory.
To me it sounds like the union just got its foot in the door at Tesla Germany and we're not at the point yet where organized action like a strike is feasible. It's worth mentioning that German employment law prohibits a company from hiring temp workers to take over the job of a striking employee, at the threat of a fine of up to €500k. On the other hand, there are strict laws around strikes for workers too, e.g. solidarity strikes are prohibited.
