I used to have one in my flat. For about two years it worked perfectly, but somehow something went wrong and I noticed too late that something was off. The pH (acidity) was wrong for some reason, which resulted in the worms dying. I bought new ones and managed to get it up and running again, only to get a real bad infestation with fungus gnats after a while, which soon were all over the flat.
When they work, worm farms are a great source if absolutely fabulous compost (for which you have to find a use - it’s way more than your balcony could handle). But you have to constantly monitor moisture, temperature, acidity, and look for any larvae of bugs you don’t want. And read up on what to do to fix any problems as early as possible.
I decided to do without after the second failure because we have curbside collection of bio waste, and the worms were just an interesting experiment. It was fun, though.
Happened to a lot of our appliances when we lived in an area with extremely soft water, which can be very corrosive. Some plastics seem to be more durable than others.