Microsoft warned users of a new known issue that may cause Word for Windows to delete some documents instead of saving them.

As the company explains, this bug only impacts users of Word for Microsoft 365 version 2409, build 18025.20104. Furthermore, this problem only arises when users close Word after editing and are prompted to save. After saving their changes this way, the file may disappear.

On impacted systems, the known issue causes locally saved files to be deleted after saving if the filenames include the symbol # or have a capitalized file extension, such as .DOCX or .RTF.

Redmond confirmed the issue after widespread user reports complaining that Microsoft Word started deleting some of their saved files.

Microsoft’s Word team is investigating the issue. Until a fix is available, affected users can take several steps to work around it, including checking the recycle bin, as the deleted file may be recoverable from there.

They can also manually save their documents before attempting to close Word. According to Redmond’s tests, “the issue occurs after saving when prompted on clicking X to close Word. It does not currently reproduce when manually saving before close.”

Additionally, those affected by this bug can enable the “Don’t show the Backstage when opening or saving files with keyboard shortcuts” setting from File > Options > Save.

Another temporary fix is to revert to the previous version until a fix is rolled out by opening a new Command Prompt window with administrator privileges from the Windows search box, pasting the following commands, and hitting Enter after each:

cd %programfiles%Common FilesMicrosoft SharedClickToRun

officec2rclient.exe /update user updatetoversion=17928.20156

Last month, Redmond fixed another known issue that affected Microsoft 365 apps like Outlook, Word, Excel, and OneNote and caused them to crash while typing or spell-checking a text.

Microsoft also shared temporary workarounds in August for known issues triggering Gmail sign-in issues for classic Outlook users and causing Outlook to crash after opening.