Dropbox web keeps dropping uploads after a few minutes saying I have no internet

Since I haven't seen a resolution in this discussion, I'll post and say I have the same problem with synching from a Windows 10 machine (not a Mac!) on both the desktop app and through the website via the browser (I've tried Chrome, Firefox, and Opera). I've had problems with files of all sizes--nothing bigger than a couple hundred MB--but currently, I'm running into the "Uploads paused" brown banner with a message near the filename "Paused - no internet" for 469K or 1015K PDFs!

I don't have any VPNs or firewalls that traffic is going through at home. We had to switch to cable internet (Xfinity Comcast) which shouldn't be restricting traffic to Dropbox domains. It has slower upload speeds, but testing shows it's typically ~20-30 Mbits/sec so a megabyte-sized file should not be an issue.

In these situations when the upload has "paused", I'll cancel and retry. Sometimes I'll walk away from the computer and eventually the file gets synch'ed up perhaps hours later. But it's pretty frustrating to see that 20% of a 1 MB file has uploaded after 1 min, but then the browser is stuck on the rest of the minuscule file before Dropbox gives up with the brown banner of death:

I regularly upload gigabyte-sized videos to YouTube without an issue with my current network configuration. Is there something fundamentally wrong with how Dropbox is talking to its servers from my computer?