Well I couldn't reproduce it on the VM, but after some kernel debugging I guessed that it was a problem with one of my 'cloud' drives, and it turned out that it was a problem with OneDrive. I unlinked my account (ie logged out of OneDrive), and then relinked (logged back in), and the problem seems to have gone away. I also moved the 'old' OneDrive folder away so that a new one was created. I'd be curious to know if this helps your errant laptop!