It appears the problem only arises when connected with a modem and not with a router. It follows that, if one connects to the internet with a modem, it would be advisable not to upgrade to the Creator's Update yet.
If you're connecting to the internet using a 3G/LTE dongle instead of regular WiFi, this is a known issue, but it's intentional. Microsoft pulled a lot of the old supported network configurations supported in Windows 10 for USB cellular modems and rewrote or replaced most of them, so a lot of older USB dongles now no longer work properly. You'd have to wait for Fall Creators Update to see any improvement, and hope that the modem vendor updates their drivers and configurations in time for that.
What's the difference between a modem and a router?
In Microsoft's terminology today, "modems" to them means the 3G/4G USB dongles. Devices like a MiFi work just fine, but the USB dongles, particularly older ones, aren't as well supported anymore.
This is also why some older 3G PCIe cards in laptops are beginning to show configuration issues and driver problems with Windows 10 after upgrading to 1703. Microsoft had a massive whitelist of supported configurations in the past, and they trimmed it with 1703 to filter out all the old modems on unused bands or that didn't have full feature support for the Windows 10 networking stack.