Do you have your preview pane turned on for Windows Explorer?
The reason that I say this is that I think that the system takes a LOT longer to release the memory for that folder if the preview pane is on.
Ever since I have turned the preview pane off, I have not had the issue.
I never use preview pane in windows. This most specifically due to the well known windows bug where as windows does not release cached just like SW doesn't release communication with a folder...
Perhaps this is a network thing the SW has... Why do I say this? I've always used SW on a network when saving files (sometimes vault, sometimes not). Vault doesn't have an issue with SW in the context of this thread though.