Some users are experiencing lots of files being made in C:\ProgramData\Microsoft\Windows Defender\Scans\History\Store folder
The error is known by Microsoft and is caused by the MsMpEng.dll. A fix to solve this will be available for all Windows 10 versions on Thursday 05/6/21 module update 1.1.18100.6.
If you like to empty out the store folder, you can do so without causing any harm to your system. There can be an excessive amount of files present, sometimes up to 25000 files or more that shouldn’t be there.
In case you can’t find the folder to check this for yourself, set hidden items to active in the File Explorer, and all will show up.
The Windows Defender version affected by this is 1.1.18100.5.
Apparently this problem will be fixed in Module version 1.1.18100.6.