When launching Arma 3 for the first time trough the launcher you have to accept the Battleye EULA.
On my Screen (details below) the popup opens outside of the normal window area so one is not able to click accept easily. This can be solved by clicking and moving around but might be really annoying for new players
Sine i dont know how to unaccept the EULA (without uninstalling) i only experienced this bug two times, once when launching the first time on my newly installed OS and once after moving the steam install location but since it was the same both times i guess it could be reproduced every time with my setup.
OS: Windows 10 Pro 64bit
Monitor Resuolution: 3840x2160
Windows Text Scaling: 150%