If the MagicSync file list contains any hidden files (filenames beginning with a dot in my case) the ability to collapse folders is broken. The collapsing seems to get "stuck" on the first hidden file it encounters, and won't hide anything below it.
In the attached screenshot, my top level folder is wp-content. If I attempt to collapse it, this it what happens. It gets hung up on .travis.yml and everything lower on the list remains visible.