Windows Defender keeps finding threat in a file I shift deleted, what shall I do ?

Hi, mystifiedgum,
Sorry to hear you're experiencing this issue.

This could be a problem in the Windows Defender protection history when a threat is already removed and keep showing the alert. Clearing the Windows Defender history should fix this problem.

Step 1:
1-Right-click on Start and click on Run
2-Type: C:\ProgramData\Microsoft\Windows Defender\Scans\History and click on OK
3-Open the Service folder, select all files inside it and delete them
4-Close the file explorer

Step 2:
1-Click on Start, search for Windows Security, and click on that
2-Click on Virus & Threat protection then click on Manage settings
3-Toggle the button to Off and then to On again, for Real-Time protection and Cloud-delivered protection

Then perform a Windows Defender offline scan, you can see how to do it at this link.
https://support.microsoft.com/en-us/windows/hel...