Updating 1809 keeps "failing" (after Dec 14 2018)

I got myself a testing mashine which I keep updating since W10 release but now it seems to have an issue with 1809.

Symptoms:

1) Windows 10 "Check for updates" only returns updates for 1803 whenever available, however keeps informing that MS distributes the new update ...

2) Windows 10 "Update assistant" offers 1809. It does complete job with restarts (even multiple) and then just boots to windows when its done. However there is no change to the system which keeps to stay on 1803. No errors, no notifications, no popus, not even an error in event viewer ... at least one I can relate to update failure.

Already performed:

1) Troubleshoot - Windows Update: This one keeps finding pending updates, but the fix is doing nothing

2) Did perform complete "Disk cleanup" with elevated rights ...

3) Did perform cleaning the update related folders (stopping update related services, doing the cleaning, restarting services and rebooting). Even after all of this I am back at point 1 troubleshooting.

So as this is a testing machine I don't really need to clean install. I would first like to see it updating itself.

Any ideas I can try?

Thanks for all help in this I believe too common issue over past few weeks.

UPDATE:

Log files from

    C:\$WINDOWS.~BT

    \Rollback logs

    setuperr.log
    Error SP CSetupPlatformOSSwitchCheckpoint::Rollback: Failed to read the rollback GUID from file: C:\$WINDOWS.~BT\Sources\Rollback\rollbackinfo.ini. Error: 0x00000002[gle=0x00000002]

    setupact.log
    Warning ExtractBugCheckInfo: Valid Dump/ Signature not found, error 0x00000490 
    Warning ExtractBugCheckInfo: Unable to find file C:\tmpgfile.sys, error 0x00000002 
    Info SP No crash detected. Try to get the binary info of last crash dump.
    Info SP Fail to find the registry key of last crash dump. Error: 0x00000002
    Info SP Cannot recover the system.
    Error SP CSetupPlatformOSSwitchCheckpoint::Rollback: Failed to read the rollback GUID from file: C:\$WINDOWS.~BT\Sources\Rollback\rollbackinfo.ini. Error: 0x00000002[gle=0x00000002]

    \Panther logs
    setuperr.log
    ....quite a lot errors any particular?
    https://pastebin.com/PB0Mrmaw

    setupact.log
    37MB ... a big one