I am seeing a similar issue, but the thumbnails seem to be not showing only for OneDrive folders which are synced. E. g., we have configured to sync Known folders (Desktop, Documents and Pictures) to OneDrive. Any image on these locations doesn't seem to show thumbnails. All other locations work fine.

I saw a few users report this issue as a bug with OneDrive and turning off 'Files on Demand' fixes it, but interestingly for us this issue is seen only on an OSOT optimised image. 

Looking at the latest OSOT tool, I don't see a setting to disable thumbnails, but not sure if its doing it without showing in the OSOT UI.

If anybody has any inputs on how to resolve this, please help.