My computer is a DELL Optiplex 3020. Both recent cumulative updates (KB5018410 and KB5016616) have failed on installation. The code is 0x800f0845. I have tried all the suggested things to try to get the update to go through up to an in-place update. All other updates go through with no problem. Just the cumulative updates. I have version 21H2 build 19044.1826.
A solution has been found. See this thread.