Thanks so much Todd,
Really appreciate you taking the time to respond. I would share the footage, but I am in a very remote location, where email barely works (never mind uploading any video clip). I’m very reassured by what you say. It may be that I just expected to make a mistake- and then just imagined that the footage doesn’t look quite ‘normal’ with the movement and speech (almost as if there was a tiny lag).
If this is not necessarily an incorrect setting (and the shutter increment irrelevant in this case), then it is more likely that my laptop is just a bit overwhelmed by the 4k footage, and that this is affecting playback of the larger files. I will down-convert some more footage and look at it again. But you have given me hope!!!
Still, quite beyond the technical lesson, it reminds me that you owe it to yourself to insist on time to fully prepare before a shoot, or you let everyone down!
Best, Sara