First thing to check are your Viewer and Canvas display size. Make sure they are set to Fit to Window or smaller.
Second, screen-captured movie files often have jumbled data that results in illusions of bad framing and even confusing the playhead so that where the playhead rests is, in fact, not where the image is.
Render it to see what it truly looks like. I'm assuming you've already ascertained that the dimensions and codec of your screen-capture software are already set to match your timeline.
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