Bought 2 Fitbit charge 3 devices in November 2018 ...

Bought 2 Fitbit charge 3 devices in November 2018 at the Frankfurt airport. A few months later they both developed black lines on the display and eventually went blank. They were replaced. In December, the same problem starts, this time, we are out of warranty and nothing can be done. We are stuck with expensive devices that are useless. 1 year 1 month, 4 devices developing the same issue. Such a short lifespan indicates faulty devices were manufactured.
The Fitbit community page shows many people are going through the same predicament. What a let down!