Very strange issue - Site pages showing up in a document library when viewed in OneDrive app?

If I had to guess it's that pesky document library webpart as usual. I don't have the updated one so I can't prove my theroy, but you get a sync button now on it. And when you click Sync, your inside the context of the Site pages library "rendering the page" so it's probably picking up and syncing that library it's on based on the URL of the page your in "aka site pages" and not the contents of the library your linking too. They really shouldn't have the sync button on the library webpart cause I can see this causing issues.

That said, if you click into the library itself by clicking 'see all', or go to site contents then to the library and use the sync button there you won't have the issue because your browser URL will be to the correct library at time of clicking. Definitely seems like a bug to me for the webpart that needs fixed.

Hey StephenRice probably SharePoint team issue but it touches the sync engine so you might have inside track of testing / reporting. Seems like one of those pesky modern context issues that needs ironed out!