Dropbox stuck on downloading

My client has given me access to their dropbox which has a bunch of very large files in it that I can download and edit.

We keep running into a very annoying problem. I have to be selective about syncing, because I'm literally downloading TB of data and have to make room. Dropbox pretty regularly will start downloading the files when I change a folder from cloud to 'local', and then slow down to a crawl. I'll see it drop randomly down to KB/s and then finally nothing where it just says 'downloading X files' but makes no progress (even after waiting a while). I've tried re-installing multiple times, resetting permission, cache, all the stuff the FAQ and base level support tells you to do to no avail. 

The only thing I've found that SOMETIMES works, is enabling a VPN. For some reason toggling a VPN will sometimes kick it into gear. But sometimes that doesn't work either. I've checked with my ISP because of the heavy use to make sure they aren't throttling the dropbox connection, and they said they are not. 

This always seems to strike when I'm coming up against a deadline and need to get these files downloaded. 

I have a lot to go, and this has been very maddening. Next time I'll tell them to just use AWS, but we're stuck for now. Hoping someone here has some bright ideas!