I think you first need to identify the problem on your machine.
Download one of those Catcin’ Sync testfiles and start working with that.
At least you will start your troubleshooting with a proper 100% issue-free test file.
(Pretty much all files/projects that I received from Final Cut have an offset of 2 frames, so even with 2pop, it might be the video operator/application that is at fault.)
If you are running video on a separate monitor (full screen), then very possibly it is that screen/monitor and or the split box/adapter/whatever that causes the problem. So try to figure out what is happening where and when, and go from there.
Fredo