To upload files or folders I use the web interface. (I donot use the sync tool anymore for various reasons - not out of pleasantry.)
When there is an error you need to scroll through a list. In the screenshot it's 2 files, but when uploading a folder sometimes many thousands. There is no smooth & 'fine' scrolling, so "red" files can be missed easily. But also, and this is my request, there is no way to select errors. You need to scroll and review the whole list and count how many errors you saw and compare it the the mentioned number of errors. And then again, also here, the small viewport for files names are an issue.
So please Dropbox; let me select which files returned errors! (and expand the popup window & show more of the file names)