Replacing single video frames

I have a video from a Zoom conference I am trying to edit - audio (speech) is synched with the video. Sadly, not all participants mics were muted by the Zoom host so have a couple of times where the video of the "nonspeaker" was preempted by viewed who made some "noise". I can live with that sound (its brief) but want to replace the video frames (maybe 1-2 seconds) of the "nonspeaker" with frames from the speaker. I understand that the lips of speaker will not synch up with the underlying audio (his speech) for that time; that is acceptable.

I know I can separate the audio track from the video track in the timeline. But, not sure how to substitute a group of video frames of the desired speaker overwriting the video frames of the "nonspeaker". I know this type of editing can be done in more sophisticated video editing tools - which I don't have access to. Can this level of video editing be done in iMovie? I am using iMove 10.1.9.