This seems to have just started happening in the last day or so (28 Oct 2021). We don't think any new software or updates have been applied to the system and Greenshot hasn't been updated for a number of months. When using the PrtScn button, Greenshot opens, shows the crosshairs to capture a region, and displays the options menu as expected. When using the Save Directly option, the system freezes up for a number of seconds and Task Manager shows "Windows Shell Experience Host" at a very high CPU usage. Eventually, the system starts responding and there doesn't appear to be any errors in the event viewer. Not sure what changed, but though we'd report this in case others are seeing similar behavior.

Thanks!