unable to open some InDesign files on drop box

[Kate5EFB]

I keep getting an error message on SOME files when I try to open them... Not all files, just some in no specific order, etc. I have updated all my software (even trashed and re-installed InDesign).

Error message is: This file is already open by another user or another application. This file may be stored on a network server and can not be opened until the other user closes it.

We use drop box - no one else has the files open I am trying to open.... 

[BobLevine · Accepted solution]

Make sure you disable smart sync to keep all files live and available on your local drive.