S4B Client crash when conntected trought celluar connection

hello,

i'm having a strange issue with a users notebook, maybe you guys have some tipps for me what we can try.

skype for business is crashing (starting, logon, crash) when the notebook is only connected thought celluar connection.

if the user is switching e.g to a wlan connection or lan connection skype is starting working again without issues. when the user disconnects from wlan/lan and start again to work with the celluar connection, skype is crashing again. all other applications are working with celluar connection with no issues.

we've tried to clear the s4b cache, we have also tried to repair the o365 pro plus installation.

of course we also have updated the wwan drivers.

Lenovo T15 Gen1

Windows 10, 21H2

O365 ProPlus 2102 (Build 13801.21106)

event log entry:

Name der fehlerhaften Anwendung: lync.exe, Version: 16.0.13801.21092, Zeitstempel: 0x61b7a503
Name des fehlerhaften Moduls: OLEAUT32.dll, Version: 10.0.19041.985, Zeitstempel: 0xfc8f0d5b
Ausnahmecode: 0xc0000005
Fehleroffset: 0x0001cdf2
ID des fehlerhaften Prozesses: 0x337c
Startzeit der fehlerhaften Anwendung: 0x01d81750bb744dce
Pfad der fehlerhaften Anwendung: C:\Program Files (x86)\Microsoft Office\root\Office16\lync.exe
Pfad des fehlerhaften Moduls: C:\WINDOWS\System32\OLEAUT32.dll
Berichtskennung: 29652811-67c2-4de0-b22c-729613596b8c
Vollständiger Name des fehlerhaften Pakets:
Anwendungs-ID, die relativ zum fehlerhaften Paket ist: