Yesterday afternoon I installed the Sierra GM Candidate after receiving an email from Apple. I didn't really use my MacBook Pro very much after that until this morning. Everything seemed to be working fine, until I noticed that when syncing files via dropbox, the uploads were taking unusually long. At first I just thought maybe I had weak wifi signal at the moment and ignored it. As the day went on, I noticed things weren't getting any better. So I did all the usual network trouble shooting. Restarted router, backed up and deleted network prefs, etc.. Ran a speedtest and was getting 60mb/s downloads, and 8mb/s up. Yet my uploads were still going extremely slow. 30-45 minutes to upload a couple of 150mb files, that would normally take a minute or two. To rule out wifi, I plugged in directly to the router via ethernet cable, and am having the same issue. I ended up running to Starbucks because somebody was urgently waiting for some files that were taking forever to upload. Went to the Bucks that had the high speed google wifi, and still the same thing. So then I thought "oh, it must be a dropbox problem", but quickly ruled that out as I tried emailing some 8mb files that took forever, and uploaded some larger files to creative cloud that were also taking forever. So after searching around online, and finding nothing, I'm here looking for some help. Does anybody have any idea why when I run a speedtest, I'm getting the usual high speed up/down speeds, yet in reality, nothing is moving that fast?