I have noticed that if preview is not enabled then File output is not working as capturing image.
This applies also for yawcam service which Yawcam preview is not used on service.
How to fix this bug?
Added info:
If a game is full screen and even preview is activated then yawcam will not work if their is a full screen application running.
Im using Yawcam .3.5.0
I hope .3.6.0 will fix this?