Microsoft releases optional patches for Internet connection problems on Windows 10
The cumulative February update for Windows 10 caused serious internet connection problems for many machines, but especially so for those who use proxies and VPNs. Worse still, the bug affected Microsoft Teams, MS Office and Outlook, crippling the services if you used them while connected to a proxy or VPN.
To Microsoft's credit, it took on the problem more quickly than expected, and has published an optional patch to address the problem. It is worth noting that Microsoft is not distributing the patch via Windows Update. Instead, one must download it manually from Microsoft or from the Microsoft Update Catalog.
There is no one fix-all patch, either. Microsoft has published instructions for installing the relevant KB for Windows 10 1709, 1803, 1809, 1903 and 1903, which can all be accessed via this support page.