Question about Sandberg Outdoor Solar Powerbank

I have been using the device for a long time and have not noticed anything like that! The device is often charged via a solar panel and that also works. Of course, it's faster via USB. As a backup, the device is in use almost all the time, even if often only in charging mode.

So far, after one year, I have not noticed any such behaviour. However, my PowerBank is only used sporadically, but it works perfectly.