I almost never use the videopad frame by frame because it doesn't jog frame by frame. I click and drag the red line. But really that's irrelevant because I do rely on the snap cuts, and like I said earlier the problem isn't in the edit, which shows everything lining up perfectly, the problem is on export it messes itself up.
Sometimes the transitions mess up too. Like I had a clip that stuttered a frame on the cross fade transition, which again doesn't show on the edit composition or even sequence preview but shows on the export playback. Or I'd have two text clips of the same text connected the latter one I added an fx blur. On the connect, the text disappears/blinks for a single frame on the transition.