Not sure if this one is known or not: but the game doesn't run properly anymore if you pin it to the taskbar in windows 10.
It starts to run, then closes itself, shows a steam dialog, and start to run again.
Sometimes the process results in a "gems of war has crashed" error, on the first gems of war that started to run, while the second one keeps loading and plays fine (so you have 2 gems of war windows up then, one working and one with an error popup on top of it.
Running the game from the desktop shortcut works fine.
But you have to look into pinning to the taskbar, and running from there. Because it shows weird behaviour.