Buried among the release notes for the re-released build is, in which it admits:
You experience the following issues in Windows 10, version 1809:
In Windows Explorer, a red X appears on the mapped network drives.
Mapped network drives are displayed as Unavailable when you run the net use command at a command prompt.
In the notification area, a notification displays the following message: 'Could not reconnect all network drives.'
Microsoft says it'll sort out the issues "in the 2019 timeframe."
The refreshed version sparks serious issues with Trend's OfficeScan endpoint protection system, although it appears the problem is late patching from Trend, and not an issue with Microsoft, in this case.
"If a customer tries to retrieve and apply the Windows 10 October 2018 Update via Windows Update before applying the required Trend Micro Critical Patch (CP) - validated by certain driver versions - it will not be able to obtain the update for a period of 60 days from the official release of the Windows 10 October 2018 Update. Please note there will be no warning message,"
"If a customer tries to apply the Windows 10 October 2018 Update via an installation package before applying the required Trend Micro Critical Patch (CP) - again validated by certain driver versions - a warning message will appear notifying the customer to first upgrade the Trend Micro product."
Finally, if you're using a Radeon HD2000 and HD4000 graphics card from AMD, you're out of luck. The new Windows build will throw out an "INVALID_POINTER_READ_c0000005_atidxx64.dll" error code and lock the screen.
Microsoft says it's looking into the issue, and in the meantime is blocking updates to Windows systems with the hardware.