Greetings Plantman.
It seems to me like the last update downloaded the last version of OneDrive into the system but "forgot" to install it. Every attempt to run the setup (OneDriveSetup.exe file), be it from the SysWOW64 folder or downloaded from the website, gave me a message saying that a newer version was already installed and i need to first unninstall the current version in order to install it.
But the version in %localappdata%\Microsoft\OneDrive\update worked fine. Installed it and it's running perfectly, no problems with file syncs whatsowever. Just went to the folder and opened OneDriveSetup.exe.
I'll update tomorrow if the thing that happened to NealKennedy happens to me, but it makes sense to me that, in his case, he installed an older version of OneDrive and Windows Update updated it to the newer, problematic, version, thus the problem happening again.
Hope it works for you as well. Best regards.