I have two licenses and oddly one issue on each.
First is on a laptop that I often have an additional monitor attached to. Often the application does not remember which monitor I opened it on last and even more often it when minimizing then maximizing it will shift back to the laptop screen instead of the external even though the external was the last place it was.
I’ve tried to find a Windows (v10 64 bit), but have not and eM Client is the only application that this is happening to.
Second is on a desktop. eM Client always starts with the Mail and Calendar folder collapsed. I always have to click on one or the other to expand the folders.