Display mode problem

[StackTrace 10]

I have an external monitor 1920x1080 60p. When I run Arma 3 on it, the display mode turns to 59i, which is less stable.

How can I keep my monitor on 60p?

vsync in on; when I turn it off, the problem persists.

This is from my Arma3.cfg file:

forcedAdapterId=-1;

detectedAdapterId=0;

detectedAdapterVendorId=4318;

detectedAdapterDeviceId=3534;

detectedAdapterSubSysId=352327000;

detectedAdapterRevision=161;

detectedAdapterBenchmark=431;

displayMode=0;

winX=16;

winY=32;

winWidth=1024;

winHeight=768;

winDefWidth=1024;

winDefHeight=768;

fullScreenWidth=1920;

fullScreenHeight=1080;

refresh=60;

renderWidth=1920;

renderHeight=1080;

multiSampleCount=1;

multiSampleQuality=0;

particlesQuality=0;

GPU_MaxFramesAhead=1000;

GPU_DetectedFramesAhead=3;

HDRPrecision=16;

vsync=1;

AToC=0;