Zip files will not open... 'invalid'.

Hello!

I'm having a problem with zipped files from Dropbox.  Apparently, it's only affecting folders.  In a nut shell, I'm operating on a mac.  I upload video files, ranging from 1GB-10GB's in size, for my clients to download. I share hundreds of these videos each year.  I was with another service but decided to switch to Dropbox recently.  

Now, after I upload a video file or two to a folder for one of my clients, once downloaded... by myself or my client... doesn't matter if it's MAC or PC or Safari or Chrome or Firefox, etc., we all get the error message the zipped file can not be opened and is 'incomplete' or 'invalid'.  

Now, if I send a download link for an individual file, no problems.  Of course, that way, it's not zipped.  But if there's multile files, that can be a pain to copy and paste every link for each individual file within any given folder.  

I read other threads about this problem and they've been labeled 'solved' after some 'updates' by Dropbox.  But this certainly has not been my experience.  

This issue virtually renders my whole purpose for using Dropbox counterproductive.  

What is the problem with zipped folders?!

Any help would be appreciated.