I was finally able to install Big Sur 11.1 update. Safe Mode didn't work for me. Same Problems like in normal mode. I managed to install Big Sur 11.1 in Recovery Mode. All personal stuff still there. Please make sure you have a backup before. To me it is still annoying and not understandable that a company like Apple is not able to fix problems like these. Ok maybe there are not a lot of users hit by this, but for me it is very annoying to try an update 30 times because you think it will work at some point in the future. I think this is more kind of a problem with your local configuration. I guess even this should be solvable.