As to how to fix, you have to usually do a factory recovery. This varies with the model. Some don't have this implemented (really cheap W10 tablets) so we are back to the maker on how to recover.
Please folk, do not omit make and model details.
While upgrading from 1809 to 1903, battery of my tablet went down and tablet off
When I turned the tablet on again, the booting went on up to windows loading, then a flash and a black screen on which first appears briefly "trying to recover installation ..." And then "undoing changes made to your computer ..." Goes on for 1 or 2 minutes and then the tablet reboots like that in a loop for a Max that I measured of a whole night
So, how can I get back to a complete Windows functionality? Thank you very much

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