I need to disable syncing in order to save changes in Photoshop.

I'm ashamed to admit I briefly dabbled in switching away from Dropbox in 2017 or so. I found that Google Drive and OneDrive both had this issue of locking files to upload them. I do a lot of development in Python and occasionally edit video in Adobe Premiere. I found that Python pip (the package installer), npm (Node.js package installer, and Adobe Premiere all had these weird race conditions and inconsistent problems when trying to save into the sync folders of those services.

Python pip will sometimes create package folders prepended with a tilde (~) character, causing pip freeze to fail (because packages cannot contain a ~ character). This is a side-effect of a temporary package folder being locked in the middle of pip doings its thing.

Adobe Premiere will show an error message about how it failed to save the project file and require you to pick a new location for the file. You will then need to save again and pick the original location and pray it isn't locked this time.

As you can imagine, I stayed with Dropbox after seeing how bad the competitions' clients were. Unfortunately, Dropbox has changed something that makes their client behave this way. That is, Dropbox now behaves as poorly as Google Drive and Microsoft OneDrive. This bug appeared around the same time as the Smart Sync feature. I recently disabled the Smart Sync feature for my entire account, but to my dismay, the problem persists.

The problem is not consistent. It seems to be a race condition. If a temporary file gets created and deleted very quickly by a program, there's a chance that Dropbox will have locked the temporary file to upload it, and the program will crash or throw an error when it is unable to delete or rename the file. Sometimes, like in the case of Python pip, a temporary folder gets left behind that causes problems later.

Dropbox, I don't know what you changed around the time that Smart Sync was introduced, but it was a bad idea. Whatever you guys did before to sync files without locking them or causing problems was genius, and did a better job on Windows than even Microsoft themselves.

Perhaps you can make the new client do whatever your legacy client did if a customer turns off Smart Sync? Even if it is available only to Plus and up customers, that would keep us from jumping ship...

I believe the file locking "bug" is a side effect from upgrading the backend system. Google Drive and OneDrive have the file locking problem because they were designed to scale very large from the beginning. Now that Dropbox has upgraded their systems to handle large loads, they now have the same problem.

Long story short: get used to it because it's not going away, unless they can achieve what Google and Microsoft could not. I recommend not using Dropbox for "live" files. For most people that means not using Dropbox at all, or any syncing program for that matter. Consider it storage only and forget about collaboration or versioning.