Hello,
From look at the original post, it seems that you may both be using Visual Studio 2013. Could you both download Visual Studio 2015 Community and give that a try? As of 4.10 we moved over to using Visual Studio 2015 and with 4.12 we moved over to the 2015 toolchain.
If you’re on a source build you can still opt to use 2013 as your IDE but it will still require the 2015 toolchain I believe.
On that point, are you using a Binary verison of the engine (downloaded from the Epic Games Launcher) or a source build engine (downloaded from Github) when this occurs?