Can I stop QuickTime from calling down Dropbox files from the cloud?

This may well be a Dropbox issue rather than an Apple one, but I'm curious.

Whenever I launch QuickTime on my Mac, it starts to call down movie files from the cloud.

Usually it's not a problem, I can just use smart sync to put them back in the cloud, but every so often, I'm really tight on bandwidth (like when I'm trying to download something for work that's urgent) & I could do without bandwidth being taken up by an unnecessary download.

I assume it's something to do with recent files or something that's in the QuickTime buffer or some such. It's always a movie file that I'd been looking at recently.

Is there any setting I can change to stop QT from asking for files that I don't need it to ask for?