I had sync problems between my home office PC and the PC in the main office. It turned out that the problem was from making huge changes in the files synced with OneDrive and SharePoint via the OneDrive for Business program. To avoid this problem I found you should have both PC’s logged in while making large changes.
Sadly the only way to get things back in sync was to perform a reset of OneDrive and then let it download all 20G again. Glad I discovered this problem before my usage got into the multi-hundred Gigabyte range.
To perform the reset and restart run this command.
%localappdata%\Microsoft\OneDrive\onedrive.exe /reset
If OneDrive does not restart on its own in a copule minutes then run this command.
%localappdata%\Microsoft\OneDrive\onedrive.exe
From this Microsoft OneDrive community forum post.
Paul Hutchinson's Blog 