Microsoft has fixed a bug in several Microsoft 365 apps. The bug caused Word, Excel, and Outlook to crash while typing or running a spell checker. The bug was caused by old (language pack) traces from previous (Office 2016) installations or Office migration components. This problem occurred because the coexistence of Office 2016 and Microsoft 365 is not supported.
Traces of old software or migration files on a PC or laptop could cause problems. Microsoft now indicates that such traces cause spontaneous crashes of Microsoft 365 apps while typing or running spell checks.
Specifically, the crashes are in the Microsoft 365 apps: Excel, Word, Outlook, PowerPoint and OneNote. The problems occur from build 17830.20138 and higher.
Cause of crashes
According to the tech giant, the cause of the crashes lies in version differences between Office 2016 “proofing tools” and the language packs installed on the affected systems, especially when a language pack has not been updated to the latest version.
According to Microsoft, the so-called proofing tools causing the crashes are traces of previous Office installations or components of Office migration projects on the affected systems. Using both Office 2016 and Microsoft 365 side by side is not supported because of the different installation technologies.
The module causing the error differs depending on the language packages installed. Microsoft has since published an overview of the affected modules. The bug has also since been fixed.
The builds of the affected MS 365 apps that have the fix are Beta Channel: Version 2409 (Build 18021.15000), Current Channel Preview: Version 2409 (Build 18025.20000) and Current Channel: Version 2409 (Build 18025.20000. The latter version will be released on September 24 this year.
Users can test themselves
Users of Office can test themselves to see if this problem may affect them. They can search the Windows Event Viewer Application Log for Event 1000 or 1001 with 0xc0000005 exception codes.
Users are strongly advised to uninstall the Office 2016 proofing tools when using a newer Office version and install the appropriate Office language packs instead. These language packs will then be automatically updated during Office updates.
Workaround
Microsoft also offers a workaround in case Microsoft 365 apps still crash while typing or performing tasks such as spell-checking, even after installing the fixed build. Users must then run an online Office Repair procedure.
If the crashes continue after that, it is recommended to uninstall and reinstall the language pack. Microsoft has released a help document for this, referring to step 2.