I can second this problem. I run 1600x900 normally. Have tried windowed and all the resizing options. It seemed to only resize the UE4 window but not the actual game.
Noted, we can confirm that the UI breaks apart in 16:10 ratio monitor. I have added support for 1440x900 and currently looking at other problematic resolution for the next build. We will publish the build at the end of this week together with other bug fixes. Really sorry that you are experiencing this issue.
Is it possible to play the game in 1440p or 1080p on your end for now?