Word 2016: Absturz in WWLIB.DLL (0xc0000005), wenn „Neue Rechtschreibung verwenden“ deaktiviert ist

Environment: Microsoft Word 2016 MSI 64-bit, version 16.0.4266.1001, Windows 11.

Symptom: Certain older .doc files and .docx files using an older compatibility mode crash Word with 0xc0000005 in WWLIB.DLL. The same documents open successfully in Word Safe Mode, in a fresh Windows user profile, or after converting them to the current Word format.

Root cause found by A/B testing:

In Word Options, disabling the German proofing option “Neue Rechtschreibung verwenden” creates:

HKEY_CURRENT_USER\Software\Microsoft\Shared Tools\Proofing Tools\1.0\Office

GermanLanguageOptions = 1 (DWORD)

With GermanLanguageOptions=1, affected old/compatibility documents reproducibly crash Word.

If the option is enabled again, or the GermanLanguageOptions value is removed/renamed, the same documents open normally.

Reproduction:

1. Enable “Neue Rechtschreibung verwenden” → affected document opens normally.
2. Disable it → Word writes GermanLanguageOptions=1.
3. Restart Word and open the same document → Word crashes.
4. Re-enable the option or remove the registry value → document opens normally again.

Crash data:

WINWORD.EXE 16.0.4266.1001

WWLIB.DLL 16.0.4266.1001

Exception: 0xc0000005 ACCESS_VIOLATION

Fault offset observed: WWLIB.DLL + 0x686D70

A full ProcDump showed the access violation occurring inside WWLIB.DLL, without a third-party DLL on the relevant Word call stack.

Workaround: Leave “Neue Rechtschreibung verwenden” enabled or remove/reset