​Microsoft has fixed a known issue that causes Microsoft 365 apps like Outlook, Word, Excel, and OneNote to crash while typing or spell-checking a text.

The crashes affect users of Excel for Microsoft 365, Word for Microsoft 365, Outlook for Microsoft 365, PowerPoint for Microsoft 365, and OneNote for Microsoft 365 on Version 2407 Build 17830.20138 or higher.

Microsoft 365 customers can confirm if they’re affected by this issue by looking at the Windows Event Viewer Application Log for Event 1000 or Event 1001 with 0xc0000005 exception codes.

Redmond explained that this crash issue is triggered by the version difference between Office 2016 proofing tools and language packs installed on impacted systems when the language pack is not updated to the latest version.

“These proofing tools are probably old traces from previous installs or part of Office suite migration. Coexistence of Office 2016 side by side with M365 apps is not supported due to different installation technologies of same version,” the company explained when it first acknowledged the bug last month.

“The faulting module name will vary depending on what language packs you have installed. For example, mscss7it.dll for Italian, or mscss7de.dll, for German, with others listed here, Language identifiers and OptionState ID values in Office 2016.”

Microsoft has now fixed this known issue in the following builds for Microsoft 365 apps:

• Beta Channel: Version 2409 (Build 18021.15000)
• Current Channel Preview: Version 2409 (Build 18025.20000)
• Current Channel: Version 2409 (Build 18025.20000) (scheduled to ship on September 24th)

In addition to updating to the latest builds, users are “strongly recommended” to uninstall the Office 2016 proofing tools if they’re using a newer version of Office and install the appropriate Office language packs instead. The Office language packs will also automatically update on Office updates.

However, if your Microsoft 365 apps still close unexpectedly while typing or using authoring features like spell check after installing the fixed build, you must perform an online Office repair using this procedure.

​If the Office apps keep crashing, you’ll need to uninstall and reinstall the language pack by following the steps detailed in this support document under “Step 2: Configure Microsoft 365 language.”

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