Yes, strange, I'm using Intel 4000 Graphics with i7-3770 cpu. Capturing with av.io HD Epiphan device (appears as camera). Source is 1080p,23.976fps, 720p source acts the same way. I set Vmix to 1080p with 1920x1080 for Display and Camera input resolution. Vmix starts capturing and then randomly the main display or the small windows will show frame drops but checking the Statistics there are no frame drops! After a while, the display frame drops disappear and it's capturing good again. If I record, the display frame drops also get recorded. If I pause my source for 2 seconds, then start it again, the display frame drops disappear and it's good again. If I pause my source for only 1 second, then start again, the display frame drops are still there. So what is happening. Is it the Intel Graphics running out of buffer or what?

Well, maybe, but I am running 2 firmware versions ahead of what is on their site. They have been working to make the device work at 23.976 and 29.97fps. When using the firmware on their site, I can plainly see frame drops and stuttering, that does not occur with the latest firmware I am testing. Audio and Video remain in perfect sync also. So...it's strange what's going on. Maybe I need to test with another capture software. I tried VLC before Vmix and it didn't work. Any other capture app you can suggest just to test this?

Update - Tried with OBS, and the same thing happens.