Since you don't say what the error message number is, I'm guessing, but I
would imagine the detections are either in an archive file (zip type
compressed file) which Defender doesn't remove, since such files could
contain other wanted/needed information, or they are in a restore folder
which also isn't touched by Defender, or they are in a quarantine folder.
All occurrences are harmless in that state but could cause a problem if
uncompressed or restored.
You should see what files are involved by examining the system event log:
Do a start, run, eventvwr.msc, **click OK**, then click on
**System**, then View, then Filter, and scroll down the " event source"
control to reach Windefend, that will give you a view of just Windows
Defender-related events.
Look for events with yellow triangles
Then make a decision as to either deleting/ignoring/manually cleaning them
or in the other case emptying your restore folder and creating a new
restore point as described in these forums.
If the four don't match this description, let us know what the error number
is and what files are involved from the event log.