This has been happening to me ever since I updated my game to version 1.36.104.1020 (the one that fixed Error Code 102). Whenever I take a screenshot in my game (whether in CAS, live or build mode), ...
That you use another AV does not mean that Windows Defender is turned off (it did in previous versions). If your Virus & Threat protection looks like the image then it is turned on. Click on the arrow beside "Windows Defender Antivirus Options" there you can turn off Windows Defender. Or you can click Virus and Protection settings. There you can turn off just the folder protection.
Also check If Avast has an option to protect folders it may be called Ransom Ware Protection.
Notice that the above directions are only valid for a fully updated Windows 10. Before The Fall Creators update it did not have this.
That you use another AV does not mean that Windows Defender is turned off (it did in previous versions). If your Virus & Threat protection looks like the image then it is turned on. Click on the arrow beside "Windows Defender Antivirus Options" there you can turn off Windows Defender. Or you can click Virus and Protection settings. There you can turn off just the folder protection.
Also check If Avast has an option to protect folders it may be called Ransom Ware Protection.
Notice that the above directions are only valid for a fully updated Windows 10. Before The Fall Creators update it did not have this.
I'm on Windows 7 so when I click on Windows Defender this pops up so I think it's off.
Avast does have a Ransomware Shield but I don't have it because my Avast isn't upgraded.