Good news from Microsoft, they got straight back to me. Still waiting to hear from Avira. I ran it through VirusTotal and found three other antiviruses that would bring back a false positive, and one of those three has cleared it to. So 2 out of 5 done!
Here is Microsoft's message below:
Analyst comments:
We have removed the detection.
Please follow the steps below to clear cached detection and obtain the latest malware definitions.
1. Open command prompt as administrator and change directory to c:\Program Files\Windows Defender
2. Run “MpCmdRun.exe -removedefinitions -dynamicsignatures”
3. Run "MpCmdRun.exe -SignatureUpdate"
Alternatively, the latest definition is available for download here: https://www.microsoft.com/en-us/wdsi/definitions
Thank you for contacting Microsoft.