Microsoft has confirmed a bug in Word for Windows that can send PDFs to an unexpected local folder instead of the SharePoint Online location users selected. The issue appears after updating to Word version 2609, when using Save or Save As, choosing PDF as the file type, and picking a SharePoint location.
Instead of appearing in SharePoint, the file is written to C:\Users[username]\AppData\Local\Microsoft\Windows\INetCache\Content.MSO with a random filename. Word gives no error, so users may not realize the save went astray. Microsoft says the Export option or saving to a different location avoids the problem.
The Register asked Microsoft about a fix but has not received a response. Some affected users report that rolling back the update resolves the issue. The bug adds to a string of recent Microsoft 365 and Windows problems, including a paste glitch in Excel, deactivated Office 2016/2019 licenses, and data deletion before retention expiry.