When not connected to the internet, I recently discovered that moving files into a dropbox folder, render them unusable while offline. It appears to be trying to sync them, but obviously can't, while offline. However I then can not open the files or subsequently move them elsewhere. I just get an infinite "copying" progress bar.
When computer is back on the internet, then files then sync as normal, but this is a huge show stopper, and resulted in a days work lost, as I couldn't open the files I needed. Please remember that not everywhere has 24 hour access to the internet!
I am now transitioning to using a NAS. This just can't happen again.
This never used to be a problem, however this seems to now be a problem after updating the mac desktop app and it moving my Dropbox folder to the library folder.
Also, now the app seems to continuously sync, even when closed (by choosing quit from the menu). I need to control bandwidth use, and will use the "pause sync" instead, but this is another change I discovered the bad way!