I do not know whether this is the source of my problem, but I have just checked Windows update and I have been upgraded to version 1809 10.017763.
I understood that Microsoft had withdrawn this update from its update servers, so apparently my machine must have updated before they did that. I have to say that in my normal work I had not realised that this had happened as I have had no problems at all.
I have had a look to see if I can find any mention of OneDrive issues on the new build, but so far have not found any.
If I can summarize what I have found with OneDrive and Explorer and Opus on my computer.
The scenario is that I have a folder of PDF files I want to keep on the cloud and download back to my machine on request.
Use save space to remove files from local disc
select a file and tell the system I want to open it in Adobe Acrobat reader
Explorer downloads the files and it opens in Reader
Use save space again to put the file back into the cloud.
I take this to be accepted and acceptable behaviour for OneDrive
Open the OneDrive folder contains the PDFs which are stored in the cloud
Immediately Opus begins to download every single PDF in the folder without being requested to do so.
Cancelling the operation makes no difference. You can look at the Lister and watch Opus bring each and every file back to my One Drive folder on the PC.
I have folders in the cloud on OneDrive that contain hundreds of images, I simply cannot countenance looking at them in Opus in case this unstoppable download procedure starts and cannot be stopped.
I have just found the following:
This is interesting, because I used this facility to move my OneDrive folder from my small SSD to my main drive.
However, I did not suffer any data loss in the upgrade