multiple device sync (?)

Hi there, 

Welcome to the Box Community, I'm happy to help!

Do you recall moving items from your Box Sync folder to outside like your desktop or anywhere else outside of Box Sync folder? If so, moving items outside of the Box Sync folder is equivalent to items being 'Deleted' in Box. 

Also, I'd like to confirm if you installed  Box Sync on your new Mac from using disaster recovery tools (i.e. Time Machine, Carbon, Genie Timeline) which uses "backup", "restore", or "sync" function? These functions should not be used to move Box Sync content from one device to another or install Box Sync as this could cause issues such as deletion or duplication of items in your Box account. We recommend to use the instructions for reinstalling Box Sync on a new device as mentioned on this page: https://support.box.com/hc/en-us/articles/360044195033-Reinstall-Box-Sync-on-a-New-Computer

1. Agree and understand: That which I remove from the boxsync folder is also deleted from app.box.com

2. I used no recovery tools, time machine or migration assistant.  ***My intention was for box sync to be my "migration assistant" but that assumption of mine was flawed.***. Instead of filling the new boxsync folder on the new device with the files, folders in app.box.com, it started deleted the app.box.com files.

Episode 2

When I noticed that the files were being deleted from app.box.com, I paused box sync on both devices.  Later I resumed boxsync on the old established device and it started to sync with app.box.com, by deleting the files that were deleted from app.box.com earlier.  So the whole thing is syncing to the state of the new empty device if I let it run unattended.

What do you advise?

Episode 3

The new device was restarted (reboot) and the pause before restart was resumed.  This deleted nearly all of the thousands of files off of the cloud (app.box.com).  As I mentioned in previous post, box wants to delete files not found on the new device, and since the new device is empty to start off, that means everything drops out of the cloud.  Shaking my head

Episode 4

Being a good sport, I deleted box sync and then installed box drive (https://www.box.com/resources/downloads) to the old established computer.  I copied one folder from a safe place that box can't touch to the box drive to see what would happen.

The one test folder went up into the box cloud.  So far so good.

Then I deleted boxsync and installed Box Drive on the new empty device.  Well it loaded nearly all of what was deleted in the old boxsync (thousands) into the Box Drive(???) even though it's not in the cloud anymore (less than a dozen files and folders left in the "All Files" level so it's easy to account).  But it is gradually deleting everything out of the files (I watch the folder timestamps to see the before and after).  

Puzzling huh?

Add to that, that the test folder just emptied on the Box Drive of the new device even though there's still 300+ files in that very folder on app.box.com. 

I'm not sure why this wasn't a problem with two local devices (macbook and samsung phone) using box app/box sync, but adding a third device (macbook #2) is too much for box drives/apps to handle.

What do you advise?